An Open Interface for Network Programming under Microsoft Windows
From Web (09.10.1996)
Windows Sockets API
This HTML version of the Windows Socket 1.1 Specification is provided
by Mark Towfiq. It may be freely redistributed, either as provided or
in modified form. Winsock providers may integrate it into their
product documentation without incurring any obligation.
Acknowledgements
I am indebted and thankful to:
-
Joel Golberger of
InfoMagic, Inc. for the work he did on the
Windows Help version of the Windows Sockets
Specification. I used his .RTF file as
the source file for this document.
-
Chris Hector of
Cray Research Inc. for his package
rtftohtml,
which was used to generate this document.
Mark Towfiq
(towfiq@East.Sun.Com)
Table of Contents
Copyright (c) 1992 by Martin Hall, Mark Towfiq
Geoff Arnold, David Treadwell and Henry Sanders
All rights reserved.
This document may be freely redistributed in any form, electronic or otherwise,
provided that it is distributed in its entirety and that the copyright and this
notice are included. Comments or questions may be submitted via electronic
mail to WinSock@MailBag.Intel.Com.
Requests to be added to the Windows
Sockets mailing list should be addressed to
MajorDomo@MailBag.Intel.Com.
This specification, archives of the mailing list, and other information on
Windows Sockets are available via anonymous FTP from the host
SunSite.UNC.Edu,
directory /pub/micro/pc-stuff/ms-windows/winsock.
Questions about products conforming to this specification should be addressed
to the vendors of the products.
The authors would like to thank their companies for allowing them the time and
resources to make this specification possible: JSB Corporation, Microdyne
Corporation, FTP Software, Sun Microsystems, and Microsoft Corporation.
Special thanks should also be extended to the other efforts contributing to the
success of Windows Sockets. The original draft was heavily influenced by
existing specifications offered and detailed by JSB Corporation and NetManage,
Inc. The "version 1.0 debate" hosted by Microsoft in Seattle allowed many of
the members of the working group to hash out final details for 1.0 vis-a-vis.
Sun Microsystems was kind enough to allow first time implementors to "plug and
play" beta software during the first Windows Sock-A-Thon of Windows Sockets
applications and implementations at Interop Fall '92. Microsoft has shared
WSAT (the Windows Sockets API Tester) with other Windows Sockets implementors
as a standard Windows Sockets test suite to aid in testing their
implementations. Finally, Sun Microsystems and FTP Software plan to host the
Windows Sock-A-Thon II in Boston February '93.
Without the contributions of the individuals and corporations involved in the
working group, Windows Sockets would never have been as thoroughly reviewed and
completed as quickly. In just one year, several competitors in the networking
business developed a useful specification with something to show for it! Many
thanks to all which participated, either in person or on e-mail to the Windows
Sockets effort. The authors would like to thank everyone who participated in
any way, and apologize in advance for anyone we have omitted.
List of contributors:
Martin Hall (Chairman) JSB Corporation martinh@jsbus.com
Mark Towfiq (Coordinator) Microdyne Corporation towfiq@microdyne.com
Geoff Arnold (Editor 1.0) Sun Microsystems geoff@east.sun.com
David Treadwell (Editor 1.1) Microsoft Corporation davidtr@microsoft.com
Henry Sanders Microsoft Corporation henrysa@microsoft.com
J. Allard Microsoft Corporation jallard@microsoft.com
Chris Arap-Bologna Distinct chris@distinct.com
Larry Backman FTP Software backman@ftp.com
Alistair Banks Microsoft Corporation alistair@microsoft.com
Rob Barrow JSB Corporation robb@jsb.co.uk
Carl Beame Beame & Whiteside beame@mcmaster,ca
Dave Beaver Microsoft Corporation dbeaver@microsoft.com
Amatzia BenArtzi NetManage, Inc. amatzia@netmanage.com
Mark Beyer Ungermann-Bass mbeyer@ub.com
Nelson Bolyard Silicon Graphics, Inc. nelson@sgi.com
Pat Bonner Hewlett-Packard p_bonner@cnd.hp.com
Derek Brown FTP Software db@wco.ftp.com
Malcolm Butler ICL mcab@oasis.icl.co.uk
Mike Calbaum Frontier Technologies mike@frontiertech.com
Isaac Chan Microsoft Corporation isaacc@microsoft.com
Khoji Darbani Informix khoji@informix.com
Nestor Fesas Hughes LAN Systems nestor@hls.com
Karanja Gakio FTP Software karanja@ftp.com
Vikas Garg Distinct vikas@distinct.com
Gary Gere Gupta ggere@gupta.com
Jim Gilroy Microsoft Corporation jamesg@microsoft.com
Bill Hayes Hewlett-Packard billh@hpchdpc.cnd.hp.com
Paul Hill MIT pbh@athena.mit.edu
Tmima Koren NetManage, Inc. tmima@netmanage.com
Hoek Law Citicorp law@dcc.tti.com
Graeme Le Roux Moresdawn P/L -
Kevin Lewis Novell kevinl@novell.com
Roger Lin 3Com roger_lin@3mail.3com.com
Terry Lister Hewlett-Packard tel@cnd.hp.com
Jeng Long Jiang Wollongong long@twg.com
Lee Murach Network Research lee@nrc.com
Pete Ostenson Microsoft Corporation peteo@microsoft.com
David Pool Spry, Inc. dave@spry.com
Bob Quinn FTP Software rcq@ftp.com
Glenn Reitsma Hughes LAN Systems glennr@hls.com
Brad Rice Age rice@age.com
Allen Rochkind 3Com -
Jonathan Rosen IBM jrosen@vnet.ibm.com
Steve Stokes Novell stoke@novell.com
Joseph Tsai 3Com joe_tsai@3mail.3com.com
James Van Bokkelen FTP Software jbvb@ftp.com
Miles Wu Wollongong wu@twg.com
Boris Yanovsky NetManage, Inc. boris@netmanage.com
The Windows Sockets specification defines a network programming interface for
Microsoft Windows which is based on the "socket" paradigm popularized in the
Berkeley Software Distribution (BSD) from the University of California at
Berkeley. It encompasses both familiar Berkeley socket style routines and a
set of Windows-specific extensions designed to allow the programmer to take
advantage of the message-driven nature of Windows.
The Windows Sockets Specification is intended to provide a single API to which
application developers can program and multiple network software vendors can
conform. Furthermore, in the context of a particular version of Microsoft
Windows, it defines a binary interface (ABI) such that an application written
to the Windows Sockets API can work with a conformant protocol implementation
from any network software vendor. This specification thus defines the library
calls and associated semantics to which an application developer can program
and which a network software vendor can implement.
Network software which conforms to this Windows Sockets specification will be
considered "Windows Sockets Compliant". Suppliers of interfaces which are
"Windows Sockets Compliant" shall be referred to as "Windows Sockets
Suppliers". To be Windows Sockets Compliant, a vendor must implement 100% of
this Windows Sockets specification.
Applications which are capable of operating with any "Windows Sockets
Compliant" protocol implementation will be considered as having a "Windows
Sockets Interface" and will be referred to as "Windows Sockets Applications".
This version of the Windows Sockets specification defines and documents the use
of the API in conjunction with the Internet Protocol Suite (IPS, generally
referred to as TCP/IP). Specifically, all Windows Sockets implementations
support both stream (TCP) and datagram (UDP) sockets.
hile the use of this API with alternative protocol stacks is not precluded
(and is expected to be the subject of future revisions of the specification),
such usage is beyond the scope of this version of the specification.
The Windows Sockets Specification has been built upon the Berkeley Sockets
programming model which is the de facto standard for TCP/IP networking. It is
intended to provide a high degree of familiarity for programmers who are used
to programming with sockets in UNIX and other environments, and to simplify the
task of porting existing sockets-based source code. The Windows Sockets API is
consistent with release 4.3 of the Berkeley Software Distribution (4.3BSD).
Portions of the Windows Sockets specification are derived from material which
is Copyright (c) 1982-1986 by the Regents of the University of California. All
rights are reserved. The Berkeley Software License Agreement specifies the
terms and conditions for redistribution.
This API is intended to be usable within all implementations and versions of
Microsoft Windows from Microsoft Windows Version 3.0 onwards. It thus provides
for Windows Sockets implementations and Windows Sockets applications in both 16
and 32 bit operating environments.
Windows Sockets makes provisions for multithreaded Windows processes. A
process contains one or more threads of execution. In the Windows 3.1
non-multithreaded world, a task corresponds to a process with a single thread.
All references to threads in this document refer to actual "threads" in
multithreaded Windows environments. In non multithreaded environments (such as
Windows 3.0), use of the term thread refers to a Windows process.
The Microsoft Windows extensions included in Windows Sockets are provided to
allow application developers to create software which conforms to the Windows
programming model. It is expected that this will facilitate the creation of
robust and high-performance applications, and will improve the cooperative
multitasking of applications within non-preemptive versions of Windows. With
the exception of
WSAStartup()
and
WSACleanup()
their use is not mandatory.
Windows Sockets is an independent specification which was created and exists
for the benefit of application developers and network vendors and, indirectly,
computer users. Each published (non-draft) version of this specification
represents a fully workable API for implementation by network vendors and
programming use by application developers. Discussion of this specification and
suggested improvements continue and are welcomed. Such discussion occurs mainly
via the Internet electronic mail forum winsock@microdyne.com. Meetings of
interested parties occur on an irregular basis. Details of these meetings are
publicized to the electronic mail forum.
Windows Sockets Version 1.0 represented the results of considerable work within
the vendor and user community as discussed in "
Origins
of Windows Sockets". This version of the specification was released in
order that network software suppliers and application developers could begin
to construct implementations and applications which conformed to the Windows
Sockets standard.
Windows Sockets Version 1.1 follows the guidelines and structure laid out by
version 1.0, making changes only where absolutely necessary as indicated by the
experiences of a number of companies that created Windows Sockets
implementations based on the version 1.0 specification. Version 1.1 contains
several clarifications and minor fixes to version 1.0. Additionally, the
following more significant changes were incorporated into version 1.1:
-
Inclusion of the gethostname()
routine to simplify retrieval of the host's name and address.
-
Definition of DLL ordinal values below 1000 as reserved for Windows Sockets
and ordinals above 1000 as unrestricted. This allows Windows Sockets vendors
to include private interfaces to their DLLs without risking that the ordinals
choosen will conflict with a future version of Windows Sockets.
-
Addition of a reference count to WSAStartup() and
WSACleanup(), requiring correspondences between the
calls. This allows applications and third-party DLLs to make use of a Windows
Sockets implementation without being concerned about the calls to these APIs
made by the other.
-
Change of return type of inet_addr() from
struct in_addr to unsigned long. This was required due to
different handling of four-byte structure returns between the Microsoft and
Borland C compilers.
-
Change of WSAAsyncSelect() semantics
from "edge-triggerred" to "level-triggerred". The level-triggerred semantics
significantly simplify an application's use of this routine.
-
Change the ioctlsocket() FIONBIO
semantics to fail if a WSAAsyncSelect() call
is outstanding on the socket.
-
Addition of the TCP_NODELAY socket option for RFC 1122 conformance.
To detect the presence of one (or many) Windows Sockets implementations on a
system, an application which has been linked with the Windows Sockets Import
Library may simply call the
WSAStartup()
routine. If an application wishes to be a little more sophisticated it can
examine the $PATH environment variable and search for instances of Windows
Sockets implementations (WINSOCK.DLL). For each instance it can issue a
LoadLibrary() call and use the
WSAStartup()
routine to discover implementation specific data.
This version of the Windows Sockets specification does not attempt to address
explicitly the issue of multiple concurrent Windows Sockets implementations.
Nothing in the specification should be interpreted as restricting multiple
Windows Sockets DLLs from being present and used concurrently by one or more
Windows Sockets applications.
For further details of where to obtain Windows Sockets components, see "
Windows
Sockets Components".
The following material is derived from the document "An Advanced 4.3BSD
Interprocess Communication Tutorial" by Samuel J. Leffler, Robert S. Fabry,
William N. Joy, Phil Lapsley, Steve Miller, and Chris Torek.
The basic building block for communication is the socket. A socket is an
endpoint of communication to which a name may be bound. Each socket in use has
a type and an associated process. Sockets exist within communication domains.
A communication domain is an abstraction introduced to bundle common properties
of threads communicating through sockets. Sockets normally exchange data only
with sockets in the same domain (it may be possible to cross domain boundaries,
but only if some translation process is performed). The Windows Sockets
facilities support a single communication domain: the Internet domain, which is
used by processes which communicate using the Internet Protocol Suite. (Future
versions of this specification may include additional domains.)
Sockets are typed according to the communication properties visible to a user.
Applications are presumed to communicate only between sockets of the same type,
although there is nothing that prevents communication between sockets of
different types should the underlying communication protocols support this.
Two types of sockets currently are available to a user. A stream socket
provides for the bi-directional, reliable, sequenced, and unduplicated flow of
data without record boundaries.
A datagram socket supports bi-directional flow of data which is not promised to
be sequenced, reliable, or unduplicated. That is, a process receiving messages
on a datagram socket may find messages duplicated, and, possibly, in an order
different from the order in which it was sent. An important characteristic of
a datagram socket is that record boundaries in data are preserved. Datagram
sockets closely model the facilities found in many contemporary packet switched
networks such as Ethernet.
The most commonly used paradigm in constructing distributed applications is the
client/server model. In this scheme client applications request services from
a server application. This implies an asymmetry in establishing communication
between the client and server.
The client and server require a well-known set of conventions before service
may be rendered (and accepted). This set of conventions comprises a protocol
which must be implemented at both ends of a connection. Depending on the
situation, the protocol may be symmetric or asymmetric. In a symmetric
protocol, either side may play the master or slave roles. In an asymmetric
protocol, one side is immutably recognized as the master, with the other as the
slave. An example of a symmetric protocol is the TELNET protocol used in the
Internet for remote terminal emulation. An example of an asymmetric protocol
is the Internet file transfer protocol, FTP. No matter whether the specific
protocol used in obtaining a service is symmetric or asymmetric, when accessing
a service there is a ``client process'' and a ``server process''.
A server application normally listens at a well-known address for service
requests. That is, the server process remains dormant until a connection is
requested by a client's connection to the server's address. At such a time the
server process ``wakes up'' and services the client, performing whatever
appropriate actions the client requests of it. While connection-based services
are the norm, some services are based on the use of datagram sockets.
Note: The following discussion of out-of-band data, also referred to as TCP
Urgent data, follows the model used in the Berkeley software distribution.
Users and implementors should be aware of the fact that there are at present
two conflicting interpretations of RFC 793 (in which the concept is
introduced), and that the implementation of out-of-band data in the Berkeley
Software Distribution does not conform to the Host Requirements laid down in
RFC 1122. To minimize interoperability problems, applications writers are
advised not to use out-of-band data unless this is required in order to
interoperate with an existing service. Windows Sockets suppliers are urged to
document the out-of-band semantics (BSD or RFC 1122) which their product
implements. It is beyond the scope of this specification to mandate a
particular set of semantics for out-of-band data handling.
The stream socket abstraction includes the notion of ``out of band'' data.
Out-of-band data is a logically independent transmission channel associated
with each pair of connected stream sockets. Out-of-band data is delivered to
the user independently of normal data. The abstraction defines that the
out-of-band data facilities must support the reliable delivery of at least one
out-of-band message at a time. This message may contain at least one byte of
data, and at least one message may be pending delivery to the user at any one
time. For communications protocols which support only in-band signaling (i.e.
the urgent data is delivered in sequence with the normal data), the system
normally extracts the data from the normal data stream and stores it
separately. This allows users to choose between receiving the urgent data in
order and receiving it out of sequence without having to buffer all the
intervening data. It is possible to ``peek'' at out-of-band data.
An application may prefer to process out-of-band data "in-line", as part of the
normal data stream. This is achieved by setting the socket option SO_OOBINLINE
(see
setsockopt()).
In this case, the application may wish to determine whether any of the unread
data is "urgent" (the term usually applied to in-line out-of-band data). To
facilitate this, the Windows Sockets implementation will maintain a logical
"mark" in the data stream to indicate the point at which the out-of-band data
was sent. An application can use the SIOCATMARK
ioctlsocket()
command to determine whether there is any unread data preceding the mark. For
example, it might use this to resynchronize with its peer by ensuring that all
data up to the mark in the data stream is discarded when appropriate.
The
WSAAsyncSelect()
routine is particularly well suited to handling notification of the presence of
out-of-band-data.
By using a datagram socket, it is possible to send broadcast packets on many
networks supported by the system. The network itself must support broadcast:
the system provides no simulation of broadcast in software. Broadcast messages
can place a high load on a network, since they force every host on the network
to service them. Consequently, the ability to send broadcast packets has been
limited to sockets which are explicitly marked as allowing broadcasting.
Broadcast is typically used for one of two reasons: it is desired to find a
resource on a local network without prior knowledge of its address, or
important functions such as routing require that information be sent to all
accessible neighbors.
The destination address of the message to be broadcast depends on the
network(s) on which the message is to be broadcast. The Internet domain
supports a shorthand notation for broadcast on the local network, the address
INADDR_BROADCAST. Received broadcast messages contain the senders address and
port, as datagram sockets must be bound before use.
Some types of network support the notion of different types of broadcast. For
example, the IEEE 802.5 token ring architecture supports the use of link-level
broadcast indicators, which control whether broadcasts are forwarded by
bridges. The Windows Sockets specification does not provide any mechanism
whereby an application can determine the type of underlying network, nor any
way to control the semantics of broadcasting.
The Intel byte ordering is like that of the DEC VAX, and therefore differs from
the Internet and 68000-type processor byte ordering. Thus care must be taken
to ensure correct orientation.
Any reference to IP addresses or port numbers passed to or from a Windows
Sockets routine must be in network order. This includes the IP address and
port fields of a struct sockaddr_in (but not the sin_family
field).
Consider an application which normally contacts a server on the TCP port
corresponding to the "time" service, but which provides a mechanism for the
user to specify that an alternative port is to be used. The port number
returned by
getservbyname()
is already in network order, which is the format required constructing an
address, so no translation is required. However if the user elects to use a
different port, entered as an integer, the application must convert this from
host to network order (using the
htons()
function) before using it to construct an address. Conversely, if the
application wishes to display the number of the port within an address
(returned via, e.g.,
getpeername()),
the port number must be converted from network to host order (using
ntohs())
before it can be displayed.
Since the Intel and Internet byte orders are different, the conversions
described above are unavoidable. Application writers are cautioned that they
should use the standard conversion functions provided as part of the Windows
Sockets API rather than writing their own conversion code, since future
implementations of Windows Sockets are likely to run on systems for which the
host order is identical to the network byte order. Only applications which use
the standard conversion functions are likely to be portable.
The socket options supported by Windows Sockets are listed in the pages
describing
setsockopt()
and
getsockopt().
A Windows Sockets implementation must recognize all of these options, and (for
getsockopt())
return plausible values for each. The default value for each option is shown
in the following table.
Value Type Meaning Default Note
--------------- -------------- -------------------------- --------------- ----
SO_ACCEPTCON BOOL Socket is listen()ing.
FALSE unless a listen()
has been performed
SO_BROADCAST BOOL Socket is configured FALSE
for the transmission of
broadcast messages.
SO_DEBUG BOOL Debugging is enabled. FALSE (i)
SO_DONTLINGER BOOL If true, the SO_LINGER TRUE
option is disabled.
SO_DONTROUTE BOOL Routing is disabled. FALSE (i)
SO_ERROR int Retrieve error status 0
and clear.
SO_KEEPALIVE BOOL Keepalives are being FALSE
sent.
SO_LINGER struct linger Returns the current l_onoff is 0
FAR * linger options.
SO_OOBINLINE BOOL Out-of-band data is FALSE
being received in the
normal data stream.
SO_RCVBUF int Buffer size for Implementation (i)
receives dependant.
SO_REUSEADDR BOOL The address to which FALSE
this socket is bound
can be used by others.
SO_SNDBUF int Buffer size for sends Implementation (i)
dependant.
SO_TYPE int The type of the socket As created
(e.g. SOCK_STREAM). via socket()
TCP_NODELAY BOOL Disables the Nagle Implementation
algorithm for send dependant.
coalescing.
Notes:
(i) An implementation may silently ignore this option on
setsockopt()
and return a constant value for
getsockopt(),
or it may accept a value for
setsockopt()
and return the corresponding value in
getsockopt()
without using the value in any way.
The
getXbyY()
and
WSAAsyncGetXByY()
classes of routines are provided for retrieving network specific information.
The getXbyY() routines were originally designed (in the first Berkeley
UNIX releases) as mechanisms for looking up information in text databases.
Although the information may be retrieved by the Windows Sockets implementation
in different ways, a Windows Sockets application requests such information in a
consistent manner through either the getXbyY() or the
WSAAsyncGetXByY() class of routines.
There are a few limited instances where the Windows Sockets API has had to
divert from strict adherence to the Berkeley conventions, usually because of
difficulties of implementation in a Windows environment.
socket
data type and error values
select()
and FD_*
Error
codes -- errno, h_errno & WSAGetLastError()
Pointers
Renamed
functions
Blocking
routines & EINPROGRESS
Maximum
number of sockets supported
Include
files
Return
values on API failure
A new data type, SOCKET, has been defined. The definition of this type was
necessary for future enhancements to the Windows Sockets specification, such as
being able to use sockets as file handles in Windows NT. Definition of this
type also facilitates porting of applications to a Win/32 environment, as the
type will automatically be promoted from 16 to 32 bits.
In UNIX, all handles, including socket handles, are small, non-negative
intergers, and some applications make assumptions that this will be true.
Windows Sockets handles have no restrictions, other than that the value
INVALID_SOCKET is not a valid socket. Socket handles may take any value in the
range 0 to INVALID_SOCKET-1.
Because the SOCKET type is unsigned, compiling existing source code from, for
example, a UNIX environment may lead to compiler warnings about signed/unsigned
data type mismatches.
This means, for example, that checking for errors when the
socket()
and
accept()
routines return should not be done by comparing the return value with
-1, or seeing if the value is negative (both common, and legal, approaches in
BSD). Instead, an application should use the manifest constant INVALID_SOCKET
as defined in
winsock.h.
For example:
TYPICAL BSD STYLE:
s = socket(...);
if (s == -1) /* or s < 0 */
{...}
PREFERRED STYLE:
s = socket(...);
if (s == INVALID_SOCKET)
{...}
Because a SOCKET is no longer represented by the UNIX-style "small non-negative
integer", the implementation of the
select()
function was changed in the Windows Sockets API. Each set of descriptors is
still represented by the fd_set type, but instead of being stored as a bitmask
the set is implemented as an array of SOCKETs.. To avoid potential problems,
applications must adhere to the use of the FD_XXX macros to set,
initialize, clear, and check the fd_set structures.
Error codes set by the Windows Sockets implementation are NOT made
available via the errno variable. Additionally, for the
getXbyY()
class of functions, error codes are NOT made available via the h_errno
variable. Instead, error codes are accessed by using the
WSAGetLastError()
API. This function is provided in Windows Sockets as a precursor (and
eventually an alias) for the Win32 function GetLastError(). This is
intended to provide a reliable way for a thread in a multi-threaded process to
obtain per-thread error information.
For compatibility with BSD, an application may choose to include a line of the
form:
#define errno WSAGetLastError()
This will allow networking code which was written to use the global errno to
work correctly in a single-threaded environment. There are, obviously, some
drawbacks. If a source file includes code which inspects errno for both socket
and non-socket functions, this mechanism cannot be used. Furthermore, it is
not possible for an application to assign a new value to errno. (In Windows
Sockets the function
WSASetLastError()
may be used for this purpose.)
TYPICAL BSD STYLE:
r = recv(...);
if (r == -1
&& errno == EWOULDBLOCK)
{...}
PREFERRED STYLE:
r = recv(...);
if (r == -1 /* (but see below) */
&& WSAGetLastError() == EWOULDBLOCK)
{...}
Although
error constants consistent with 4.3 Berkeley Sockets are provided for
compatibility purposes, applications should, where possible, use the "WSA"
error code definitions. For example, a more accurate version of the above
source code fragment is:
r = recv(...);
if (r == -1
&& WSAGetLastError() ==
WSAEWOULDBLOCK)
{...}
All pointers used by applications with Windows Sockets should be FAR. To
facilitate this, data type definitions such as LPHOSTENT are provided.
In two cases it was necessary to rename functions which are used in Berkeley
Sockets in order to avoid clashes with other APIs.
close() &
closesocket()
In Berkeley Sockets, sockets are represented by standard file descriptors, and
so the close() function can be used to close sockets as well as regular
files. While nothing in the Windows Sockets API prevents an implementation
from using regular file handles to identify sockets, nothing requires it
either. Socket descriptors are not presumed to correspond to regular file
handles, and file operations such as read(), write(), and
close() cannot be assumed to work correctly when applied to socket
descriptors.. Sockets must be closed by using the
closesocket()
routine. Using the close() routine to close a socket is incorrect and
the effects of doing so are undefined by this specification.
ioctl() &
ioctlsocket()
Various C language run-time systems use the ioctl() routine for purposes
unrelated to Windows Sockets. For this reason we have defined the routine
ioctlsocket()
which is used to handle socket functions which in the Berkeley Software
Distribution are performed using ioctl() and fcntl().
Although blocking operations on sockets are supported under Windows Sockets,
their use is strongly discouraged. Programmers who are constrained to use
blocking mode -- for example, as part of an existing application which is to be
ported -- should be aware of the semantics of blocking operations in Windows
Sockets. See
Blocking/Non
blocking & Data Volatility for more details.
The maximum number of sockets supported by a particular Windows Sockets
supplier is implementation specific. An application should make no assumptions
about the availability of a certain number of sockets. This topic is addressed
further in the section on
WSAStartup().
However, independent of the number of sockets supported by a particular
implementation is the issue of the maximum number of sockets which an
application can actually make use of.
The maximum number of sockets which a Windows Sockets application can make use
of is determined at compile time by the manifest constant FD_SETSIZE. This
value is used in constructing the fd_set structures used in
select().
The default value in
winsock.h
is 64. If an application is designed to be capable of working with more than
64 sockets, the implementor should define the manifest FD_SETSIZE in every
source file before including
winsock.h.
One way of doing this may be to include the definition within the compiler
options in the makefile, for example adding -DFD_SETSIZE=128 as an option to
the compiler command line for Microsoft C. It must be emphasized that defining
FD_SETSIZE as a particular value has no effect on the actual number of sockets
provided by a Windows Sockets implementation.
For ease of portability of existing Berkeley sockets based source code, a
number of standard Berkeley include files are supported. However, these
Berkeley header files merely include the
winsock.h
include file, and it is therefore sufficient (and recommended) that Windows
Sockets application source files should simply include
winsock.h.
The manifest constant SOCKET_ERROR is provided for checking API failure.
Although use of this constant is not mandatory, it is recommended. The
following example illustrates the use of the SOCKET_ERROR constant:
TYPICAL BSD STYLE:
r = recv(...);
if (r == -1 /* or r < 0 */
&& errno == EWOULDBLOCK)
{...}
PREFERRED STYLE:
r = recv(...);
if (r == SOCKET_ERROR
&& WSAGetLastError() ==
WSAEWOULDBLOCK)
{...}
The Windows Sockets specification does not mandate that a Windows Sockets DLL
support raw sockets, that is, sockets opened with SOCK_RAW. However, a Windows
Sockets DLL is allowed and encouraged to supply raw socket support. A Windows
Sockets-compliant application that wishes to use raw sockets should attempt to
open the socket with the socket() call (see section 4.1.23), and if it
fails either attempt to use another socket type or indicate the failure to the
user.
The Windows Sockets interface is designed to work for both single-threaded
versions of Windows (such as Windows 3.1) and future multithreaded versions of
Windows (such as Windows NT). In a multithreaded environment the sockets
interface is basically the same, but the author of a multithreaded application
must be aware that it is the responsibility of the application, not the Windows
Sockets implementation, to synchronize access to a socket between threads.
This is the same rule as applies to other forms of I/O such as file I/O.
Failure to synchronize calls on a socket leads to unpredictable results; for
example if there are two simultaneous calls to send(), there is no guarantee as
to the order in which the data will be sent.
Closing a socket in one thread that has an outstanding blocking call on the
same socket in another thread will cause the blocking call to fail with
WSAEINTR,
just as if the operation were cancelled. This also applies if there
is a
select()
call outstanding and the application closes one of the sockets being
selected.
There is no default blocking hook installed in preemptive multithreaded
versions of Windows. This is because the machine will not be blocked if a
single application is waiting for an operation to complete and hence not
calling PeekMessage() or GetMessage() which cause the application to yield in
nonpremptive Windows. However, for backwards compatibility the
WSASetBlockingHook() call is implemented in multithreaded versions of Windows,
and any application whose behavior depends on the default blocking hook may
install their own blocking hook which duplicates the default hook's semantics,
if desired.
The Windows Sockets specification includes the following Berkeley-style socket
routines:
accept()
An incoming connection is acknowledged and associated with an immediately
created socket. The original socket is returned to the listening state.
bind()
Assign a local name to an unnamed socket.
closesocket()
Remove a socket descriptor from the per-process object reference table. Only
blocks if SO_LINGER is set.
connect()
Initiate a connection on the specified socket.
getpeername()
Retrieve the name of the peer connected to the specified socket descriptor.
getsockname()
Retrieve the current name for the specified socket
getsockopt()
Retrieve options associated with the specified socket descriptor.
htonl()
Convert a 32-bit quantity from host byte order to network byte order.
htons()
Convert a 16-bit quantity from host byte order to network byte order.
inet_addr()
Converts a character string representing a number in the Internet standard ``.''
notation to an Internet address value.
inet_ntoa()
Converts an Internet address value to an ASCII string in ``.'' notation i.e.
``a.b.c.d''.
ioctlsocket()
Provide control for descriptors.
listen()
Listen for incoming connections on a specified socket.
ntohl()
Convert a 32-bit quantity from network byte order to host byte order.
ntohs()
Convert a 16-bit quantity from network byte order to host byte order.
recv()*
Receive data from a connected socket.
recvfrom()*
Receive data from either a connected or unconnected socket.
select()*
Perform synchronous I/O multiplexing.
send()*
Send data to a connected socket.
sendto()*
Send data to either a connected or unconnected socket.
setsockopt()
Store options associated with the specified socket descriptor.
shutdown()
Shut down part of a full-duplex connection.
socket()
Create an endpoint for communication and return a socket descriptor.
* The routine can block if acting on a blocking socket.
One major issue in porting applications from a Berkeley sockets environment to
a Windows environment involves "blocking"; that is, invoking a function which
does not return until the associated operation is completed. The problem
arises when the operation may take an arbitrarily long time to complete: an
obvious example is a
recv()
which may block until data has been received from the peer system. The default
behavior within the Berkeley sockets model is for a socket to operate in a
blocking mode unless the programmer explicitly requests that operations be
treated as non-blocking. It is strongly recommended that programmers use
the nonblocking (asynchronous) operations if at all possible, as they work
significantly better within the nonpreemptive Windows environment. Use
blocking operations only if absolutely necessary, and carefully read and
understand this section if you must use blocking operations.
Even on a blocking socket, some operations (e.g.
bind(),
getsockopt(),
getpeername())
can be completed immediately. For such operations there is no difference
between blocking and non-blocking operation. Other operations (e.g.
recv())
may be completed immediately or may take an arbitrary time to complete,
depending on various transport conditions. When applied to a blocking socket,
these operations are referred to as blocking operations. All routines which
can block are listed with an asterisk in the tables above and below.
Within a Windows Sockets implementation, a blocking operation which cannot be
completed immediately is handled as follows. The DLL initiates the operation,
and then enters a loop in which it dispatches any Windows messages (yielding
the processor to another thread if necessary) and then checks for the
completion of the Windows Sockets function. If the function has completed, or
if
WSACancelBlockingCall()
has been invoked, the blocking function completes with an appropriate result.
Refer to
WSASetBlockingHook(),
for a complete description of this mechanism, including pseudocode for the
various functions.
If a Windows message is received for a process for which a blocking operation
is in progress, there is a risk that the application will attempt to issue
another Windows Sockets call. Because of the difficulty of managing this
condition safely, the Windows Sockets specification does not support such
application behavior. Two functions are provided to assist the programmer in
this situation.
WSAIsBlocking()
may be called to determine whether or not a blocking Windows Sockets call is in
progress.
WSACancelBlockingCall()
may be called to cancel an in-progress blocking call, if any. Any other
Windows Sockets function which is called in this situation will fail with the
error WSAEINPROGRESS.
It should be emphasized that this restriction
applies to both blocking and non-blocking operations.
Although this mechanism is sufficient for simple applications, it cannot
support the complex message-dispatching requirements of more advanced
applications (for example, those using the MDI model). For such applications,
the Windows Sockets API includes the function
WSASetBlockingHook(),
which allows the programmer to define a special routine which will be called
instead of the default message dispatch routine described above.
The Windows Sockets DLL will call the blocking hook function only if all of the
following are true: the routine is one which is defined as being able to block,
the specified socket is a blocking socket, and the request cannot be completed
immediately. (A socket is set to blocking by default, but the IOCTL FIONBIO
and
WSAAsyncSelect()
both set a socket to nonblocking mode.) If an application uses only
non-blocking sockets and uses the
WSAAsyncSelect()
and/or the
WSAAsyncGetXByY()
routines instead of
select()
and the
getXbyY()
routines, then the blocking hook will never be called and the application does
not need to be concerned with the reentrancy issues the blocking hook can
introduce.
If an application invokes an asynchronous or non-blocking operation which takes
a pointer to a memory object (e.g. a buffer, or a global variable) as an
argument, it is the responsibility of the application to ensure that the object
is available to the Windows Sockets implementation throughout the operation.
The application must not invoke any Windows function which might affect the
mapping or addressability of the memory involved. In a multithreaded system,
the application is also responsible for coordinating access to the object using
appropriate synchronization mechanisms. A Windows Sockets implementation
cannot, and will not, address these issues. The possible consequences of
failing to observe these rules are beyond the scope of this specification.
The Windows Sockets specification defines the following "database" routines.
As noted earlier, a Windows Sockets supplier may choose to implement these in a
manner which does not depend on local database files. The pointer returned by
certain database routines such as
gethostbyname()
points to a structure which is allocated by the Windows Sockets library. The
data which is pointed to is volatile and is good only until the next Windows
Sockets API call from that thread. Additionally, the application must never
attempt to modify this structure or to free any of its components. Only one
copy of this structure is allocated for a thread, and so the application should
copy any information which it needs before issuing any other Windows Sockets
API calls.
gethostbyaddr()*
Retrieve the name(s) and address corresponding to a network address.
gethostname()
Retrieve the name of the local host.
gethostbyname()*
Retrieve the name(s) and address corresponding to a host name.
getprotobyname()*
Retrieve the protocol name and number corresponding to a protocol name.
getprotobynumber()*
Retrieve the protocol name and number corresponding to a protocol number.
getservbyname()*
Retrieve the service name and port corresponding to a service name.
getservbyport()*
Retrieve the service name and port corresponding to a port.
* The routine can block under some circumstances.
The Windows Sockets specification provides a number of extensions to the
standard set of Berkeley Sockets routines. Principally, these extended APIs
allow message-based, asynchronous access to network events. While use of this
extended API set is not mandatory for socket-based programming (with the
exception of
WSAStartup()
and
WSACleanup()),
it is recommended for conformance with the Microsoft Windows programming
paradigm.
Asynchronous
select() Mechanism
Asynchronous
Support Routines
Hooking
Blocking Methods
Error
Handling
Accessing
a Windows Sockets DLL from an Intermediate DLL
Internal
Use of Messages by Windows Sockets Implementations
Private
API Interfaces
WSAAsyncGetHostByAddr()
A set of functions which provide asynchronous
WSAAsyncGetHostByName()
versions of the standard Berkeley
WSAAsyncGetProtoByName()
getXbyY() functions. For example, the
WSAAsyncGetProtoByNumber()
WSAAsyncGetHostByName() function provides an asynchronous message
based
WSAAsyncGetServByName()
implementation of the standard Berkeley
WSAAsyncGetServByPort()
gethostbyname() function.
WSAAsyncSelect()
Perform asynchronous version of select()
WSACancelAsyncRequest()
Cancel an outstanding instance of a WSAAsyncGetXByY() function.
WSACancelBlockingCall()
Cancel an outstanding "blocking" API call
WSACleanup()
Sign off from the underlying Windows Sockets DLL.
WSAGetLastError()
Obtain details of last Windows Sockets API error
WSAIsBlocking()
Determine if the underlying Windows Sockets DLL is already blocking an existing
call for this thread
WSASetBlockingHook()
"Hook" the blocking method used by the underlying Windows Sockets
implementation
WSASetLastError()
Set the error to be returned by a subsequent WSAGetLastError()
WSAStartup()
Initialize the underlying Windows Sockets DLL.
WSAUnhookBlockingHook()
Restore the original blocking function
The
WSAAsyncSelect()
API allows an application to register an interest in one or many network
events. This API is provided to supersede the need to do polled network I/O.
Any situation in which
select()
or non-blocking I/O routines (such as
send()
and
recv())
are either already used or are being considered is usually a candidate for the
WSAAsyncSelect()
API. When declaring interest in such condition(s), you supply a window handle
to be used for notification. The corresponding window then receives
message-based notification of the conditions in which you declared an
interest.
WSAAsyncSelect()
allows interest to be declared in the following conditions for a particular
socket:
- Socket readiness for reading
- Socket readiness for writing
- Out-of-band data ready for reading
- Socket readiness for accepting incoming connection
- Completion of non-blocking connect()
- Connection closure
The asynchronous "database" functions allow applications to request information
in an asynchronous manner. Some network implementations and/or configurations
perform network based operations to resolve such requests. The
WSAAsyncGetXByY() functions allow application developers to request
services which would otherwise block the operation of the whole Windows
environment if the standard Berkeley function were used. The
WSACancelAsyncRequest()
function allows an application to cancel any outstanding asynchronous
request.
As noted in
Blocking/Non
blocking & Data Volatility, Windows Sockets implements blocking
operations in such a way that Windows message processing can continue, which
may result in the application which issued the call receiving a Windows
message. In certain situations an application may want to influence or change
the way in which this pseudo-blocking process is implemented. The
WSASetBlockingHook()
provides the ability to substitute a named routine which the Windows Sockets
implementation is to use when relinquishing the processor during a "blocking"
operation.
For compatibility with thread-based environments, details of API errors are
obtained through the
WSAGetLastError()
API. Although the accepted "Berkeley-Style" mechanism for obtaining
socket-based network errors is via "errno", this mechanism cannot guarantee the
integrity of an error ID in a multi-threaded environment.
WSAGetLastError()
allows you to retrieve an error code on a per thread basis.
WSAGetLastError()
returns error codes which avoid conflict with standard Microsoft C error codes.
Certain error codes returned by certain Windows Sockets routines fall into the
standard range of error codes as defined by Microsoft C. If you are NOT using
an application development environment which defines error codes consistent
with Microsoft C, you are advised to use the Windows Sockets error codes
prefixed by "WSA" to ensure accurate error code detection.
Note that this specification defines a recommended set of error codes, and
lists the possible errors which may be returned as a result of each function.
It may be the case in some implementations that other Windows Sockets error
codes will be returned in addition to those listed, and applications should be
prepared to handle errors other than those enumerated under each API
description. However a Windows Sockets implementation must not return any
value which is not enumerated in the table of legal Windows Sockets errors
given in
Error
Codes.
A Windows Sockets DLL may be accessed both directly from an application and
through an "intermediate" DLL. An example of such an intermediate DLL would be
a virtual network API layer that supports generalized network functionality for
applications and uses Windows Sockets. Such a DLL could be used by several
applications simultaneously, and the DLL must take special precautions with
respect to the WSAStartup() and WSACleanup() calls to ensure that
these routines are called in the context of each task that will make Windows
Sockets calls. This is because the Windows Sockets DLL will need a call to
WSAStartup() for each task in order to set up task-specific data
structures, and a call to WSACleanup() to free any resources allocated
for the task.
There are (at least) two ways to accomplish this. The simplest method is for
the intermediate DLL to have calls similiar to
WSAStartup()
and
WSACleanup()
that applications call as appropriate. The DLL would then call
WSAStartup()
or
WSACleanup()
from within these routines. Another mechanism is for the intermediate DLL
to build a table of task handles, which are obtained from the
GetCurrentTask() Windows API, and at each entry point into the
intermediate DLL check whether
WSAStartup()
has been called for the current task, then call
WSAStartup()
if necessary.
If a DLL makes a blocking call and does not install its own blocking hook, then
the DLL author must be aware that control may be returned to the application
either by an application-installed blocking hook or by the default blocking
hook. Thus, it is possible that the application will cancel the DLL's blocking
operation via
WSACancelBlockingCall().
If this occurs, the DLL's blocking operation will fail with the error code
WSAEINTR,
and the DLL must return control to the calling task as quickly as
possible, as the used has likely pressed a cancel or close button and the task
has requested control of the CPU. It is recommended that DLLs which make
blocking calls install their own blocking hooks with
WSASetBlockingHook()
to prevent unforeseen interactions between the application and the
DLL.
Note that this is not necessary for DLLs in Windows NT because of its
different process and DLL structure. Under Windows NT, the intermediate DLL
could simply call
WSAStartup()
in its DLL initialization routine, which is called whenever a new process
which uses the DLL starts.
In order to implement Windows Sockets purely as a DLL, it may be necessary for
the DLL to post messages internally for communication and timing. This is
perfectly legal; however, a Windows Sockets DLL must not post messages to a
window handle opened by a client application except for those messages
requested by the application. A Windows Sockets DLL that needs to use messages
for its own purposes must open a hidden window and post any necessary messages
to the handle for that window.
The
winsock.def
file lists the ordinals defined for the Windows Sockets APIs. In addition to
the ordinal values listed, all ordinals 999 and below are reserved for future
Windows Sockets use. It may be convenient for a Windows Sockets implementation
to export additional, private interfaces from the Windows Sockets DLL. This is
perfectly acceptable, as long as the ordinals for these exports are above 1000.
Note that any application that uses a particular Windows Sockets DLL's private
APIs will most likely not work on any other vendor's Windows Sockets
implementation. Only the APIs defined in this document are guaranteed to be
present in every Windows Sockets implementation.
If an application uses private interfaces of a particular vendor's Windows
Sockets DLL, it is recommended that the DLL not be statically linked with the
application but rather dynamically loaded with the Windows routines
LoadLibrary() and GetProcAddress(). This allows the application
to give an informative error message if it is run on a system with a Windows
Sockets DLL that does not support the same set of extended functionality.
This chapter presents the socket library routines in alphabetical order, and
describes each routine in detail.
In each routine it is indicated that the header file
winsock.h
must be included.
Header
Files lists the Berkeley-compatible header files which are supported.
These are provided for compatibility purposes only, and each of them will
simply include
winsock.h.
The Windows header file windows.h is also needed, but winsock.h
will include it if necessary.
Description
Accept a connection on a socket.
#include <winsock.h>
SOCKET PASCAL FAR accept ( SOCKET s, struct sockaddr FAR *
addr, int FAR * addrlen);
- s
- A descriptor identifying a socket which is listening for connections after a listen().
- addr
- An optional pointer to a buffer which receives the address of the
connecting entity, as known to the communications layer. The exact format of
the addr argument is determined by the address family established when
the socket was created.
- addrlen
- A optional pointer to an integer which contains the length of the address addr.
Remarks
This routine extracts the first connection on the queue of
pending connections on s, creates a new socket with the same properties
as s and returns a handle to the new socket. If no pending connections
are present on the queue, and the socket is not marked as non-blocking,
accept() blocks the caller until a connection is present. If the socket
is marked non-blocking and no pending connections are present on the queue,
accept() returns an error as described below. The accepted socket may
not be used to accept more connections. The original socket remains open.
The argument addr is a result parameter that is filled in with the
address of the connecting entity, as known to the communications layer. The
exact format of the addr parameter is determined by the address family
in which the communication is occurring. The addrlen is a value-result
parameter; it should initially contain the amount of space pointed to by
addr; on return it will contain the actual length (in bytes) of the
address returned. This call is used with connection-based socket types such as
SOCK_STREAM. If addr and/or addrlen are equal to NULL, then no
information about the remote address of the accepted socket is returned.
Return Value
If no error occurs, accept() returns a value of type
SOCKET which is a descriptor for the accepted packet. Otherwise, a value of
INVALID_SOCKET is returned, and a specific error code may be retrieved by
calling
WSAGetLastError().
The integer referred to by addrlen initially contains the amount of
space pointed to by addr. On return it will contain the actual length
in bytes of the address returned.
Error Codes
- WSAENOTINITIALISED
- A successful WSAStartup() must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem has failed.
- WSAEFAULT
- The addrlen argument is too small (less than the sizeof a struct sockaddr).
- WSAEINTR
- The (blocking) call was canceled via WSACancelBlockingCall()
- WSAEINPROGRESS
- A blocking Windows Sockets call is in progress.
- WSAEINVAL
- listen() was not invoked prior to accept().
- WSAEMFILE
- The queue is empty upon entry to accept() and there are no descriptors available.
- WSAENOBUFS
- No buffer space is available.
- WSAENOTSOCK
- The descriptor is not a socket.
- WSAEOPNOTSUPP
- The referenced socket is not a type that supports connection-oriented service.
- WSAEWOULDBLOCK
- The socket is marked as non-blocking and no connections are present to be accepted.
See Also
bind(),
connect(),
listen(),
select(),
socket(),
WSAAsyncSelect().
Description
Associate a local address with a socket.
#include <winsock.h>
int PASCAL FAR bind ( SOCKET s, const struct sockaddr
FAR * name, int namelen);
- s
- A descriptor identifying an unbound socket.
- name
- The address to assign to the socket. The sockaddr structure is defined as follows:
struct sockaddr {
u_short sa_family;
char sa_data[14];
};
- namelen
- The length of the name.
Remarks
This routine is used on an unconnected datagram or stream
socket, before subsequent
connect()s
or
listen()s.
When a socket is created with
socket(),
it exists in a name space (address family), but it has no name assigned.
bind() establishes the local association (host address/port number) of
the socket by assigning a local name to an unnamed socket.
In the Internet address family, a name consists of several components. For
SOCK_DGRAM and SOCK_STREAM, the name consists of three parts: a host address,
the protocol number (set implicitly to UDP or TCP, respectively), and a port
number which identifies the application. If an application does not care what
address is assigned to it, it may specify an Internet address equal to
INADDR_ANY, a port equal to 0, or both. If the Internet address is equal to
INADDR_ANY, any appropriate network interface will be used; this simplifies
application programming in the presence of multi-homed hosts. If the port is
specified as 0, the Windows Sockets implementation will assign a unique port to
the application with a value between 1024 and 5000. The application may use
getsockname()
after bind() to learn the address that has been assigned to it, but note
that getsockname() will not necessarily fill in the Internet address
until the socket is connected, since several Internet addresses may be valid if
the host is multi-homed.
If an application desires to bind to an arbitrary port outside of the range
1024 to 5000, such as the case of rsh which must bind to any reserved port,
code similar to the following may be used:
SOCKADDR_IN sin;
SOCKET s;
u_short alport = IPPORT_RESERVED;
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = 0;
for (;;) {
sin.sin_port = htons(alport);
if (bind(s, (LPSOCKADDR)&sin, sizeof (sin)) == 0) {
/* it worked */
}
if(GetLastError()!=WSAEADDRINUSE){
/* fail */
}
alport--;
if (alport == IPPORT_RESERVED/2 ) {
/* fail--all unassigned reserved ports are */
/* in use. */
}
}
Return Value
If no error occurs, bind() returns 0. Otherwise, it
returns SOCKET_ERROR, and a specific error code may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEADDRINUSE
- The specified address is already in use. (See the SO_REUSEADDR socket
option under
setsockopt().)
- WSAEFAULT
- The namelen argument is too small (less than the size of a struct
sockaddr).
- WSAEINTR
- The (blocking) call was canceled via WSACancelBlockingCall()
- WSAEINPROGRESS
- A blocking Windows Sockets call is in progress.
- WSAEAFNOSUPPORT
- The specified address family is not supported by
- this protocol.
- WSAEINVAL
- The socket is already bound to an address.
- WSAENOBUFS
- Not enough buffers available, too many connections.
- WSAENOTSOCK
- The descriptor is not a socket.
See Also
connect(),
listen(),
getsockname(),
setsockopt(),
socket(),
WSACancelBlockingCall().
Description
Close a socket.
#include <winsock.h>
int FAR PASCAL closesocket ( SOCKET s);
- s
- A descriptor identifying a socket.
Remarks
This function closes a socket. More precisely, it releases the
socket descriptor s, so that further references to s will fail
with the error WSAENOTSOCK.
If this is the last reference to the underlying
socket, the associated naming information and queued data are discarded.
The semantics of closesocket() are affected by the socket options
SO_LINGER and SO_DONTLINGER as follows:
Option Interval Type of close Wait for close?
--------------- --------------- ----------------------- ----------------
SO_DONTLINGER Don't care Graceful No
SO_LINGER Zero Hard No
SO_LINGER Non-zero Graceful Yes
If SO_LINGER is set (i.e. the l_onoff field of the linger structure is
non-zero; see
Socket
Options,
getsockopt()
and
setsockopt())
with a zero timeout interval (l_linger is zero), closesocket() is
not blocked even if queued data has not yet been sent or acknowledged. This is
called a "hard" close, because the socket is closed immediately, and any unsent
data is lost. Any
recv()
call on the remote side of the circuit can fail with
WSAECONNRESET.
If SO_LINGER is set with a non-zero timeout interval, the closesocket()
call blocks until the remaining data has been sent or until the timeout
expires. This is called a graceful disconnect. Note that if the socket is set
to non-blocking and SO_LINGER is set to a non-zero timeout, the call to
closesocket() will fail with an error of
WSAEWOULDBLOCK.
If SO_DONTLINGER is set on a stream socket (i.e. the l_onoff field of
the linger structure is zero; see
Socket
Options,
getsockopt()
and
setsockopt()),
the closesocket() call will return immediately. However, any data
queued for transmission will be sent if possible before the underlying socket
is closed. This is also called a graceful disconnect. Note that in this case
the Windows Sockets implementation may not release the socket and other
resources for an arbitrary period, which may affect applications which expect
to use all available sockets.
Return Value
If no error occurs, closesocket() returns 0.
Otherwise, a value of SOCKET_ERROR is returned, and a specific error code may
be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful WSAStartup() must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem has failed.
- WSAENOTSOCK
- The descriptor is not a socket.
- WSAEINPROGRESS
- A blocking Windows Sockets call is in progress.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall().
- WSAEWOULDBLOCK
- The socket is marked as nonblocking and SO_LINGER is set to a nonzero timeout value.
See Also
accept(),
socket(),
ioctlsocket(),
setsockopt(),
WSAAsyncSelect().
Description
Establish a connection to a peer.
#include <winsock.h>
int PASCAL FAR connect ( SOCKET s, const struct sockaddr FAR
* name, int namelen);
- s
- A descriptor identifying an unconnected socket.
- name
- The name of the peer to which the socket is to be connected.
- namelen
- The length of the name.
Remarks
This function is used to create a connection to the specified
foreign association. The parameter s specifies an unconnected datagram
or stream socket If the socket is unbound, unique values are assigned to the
local association by the system, and the socket is marked as bound. Note that
if the address field of the name structure is all zeroes,
connect() will return the error
WSAEADDRNOTAVAIL.
For stream sockets (type SOCK_STREAM), an active connection is initiated to the
foreign host using name (an address in the name space of the socket).
When the socket call completes successfully, the socket is ready to
send/receive data-
For a datagram socket (type SOCK_DGRAM), a default destination is set, which
will be used on subsequent
send()
and
recv()
calls.
On a non-blocking socket, if the return value is SOCKET_ERROR an application
should call
WSAGetLastError().
If this indicates an error code of
WSAEWOULDBLOCK,
then your application can
either:
-
Use select() to determine the completion of the connection request
by checking if the socket is writeable, or
-
If your application is using the message-based
WSAAsyncSelect() to indicate interest in connection
events, then your application will receive an FD_CONNECT message when the
connect operation is complete.
Return Value
If no error occurs, connect() returns 0. Otherwise,
it returns SOCKET_ERROR, and a specific error code may be retrieved by calling
WSAGetLastError().
On a blocking socket, the return value indicates success or failure of the
connection attempt.
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEADDRINUSE
- The specified address is already in use.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
- WSAEINPROGRESS
- A blocking Windows Sockets call is in progress.
- WSAEADDRNOTAVAIL
- The specified address is not available from the local machine.
- WSAEAFNOSUPPORT
- Addresses in the specified family cannot be used with this socket.
- WSAECONNREFUSED
- The attempt to connect was forcefully rejected.
- WSAEDESTADDREQ
- A destination address is required.
- WSAEFAULT
- The namelen argument is incorrect.
- WSAEINVAL
- The socket is not already bound to an address.
- WSAEISCONN
- The socket is already connected.
- WSAEMFILE
- No more file descriptors are available.
- WSAENETUNREACH
- The network can't be reached from this host at this time.
- WSAENOBUFS
- No buffer space is available. The socket cannot be connected.
- WSAENOTSOCK
- The descriptor is not a socket.
- WSAETIMEDOUT
- Attempt to connect timed out without establishing a connection
- WSAEWOULDBLOCK
- The socket is marked as non-blocking and the connection cannot be completed
immediately. It is possible to select()
the socket while it is connecting by select()ing it for writing.
See Also
accept(),
bind(),
getsockname(),
socket(),
and
WSAAsyncSelect.
Description
Get the address of the peer to which a socket is
connected.
#include <winsock.h>
int PASCAL FAR getpeername(SOCKET s, struct sockaddr FAR *
name, int FAR * namelen);
- s
- A descriptor identifying a connected socket.
- name
- The structure which is to receive the name of the peer.
- namelen
- A pointer to the size of the name structure.
Remarks
getpeername() retrieves the name of the peer connected to
the socket s and stores it in the struct sockaddr identified by
name. It is used on a connected datagram or stream socket.
On return, the namelen argument contains the actual size of the name
returned in bytes.
Return Value
If no error occurs, getpeername() returns 0.
Otherwise, a value of SOCKET_ERROR is returned, and a specific error code may
be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEFAULT
- The namelen argument is not large enough.
- WSAEINPROGRESS
- A blocking Windows Sockets call is in progress.
- WSAENOTCONN
- The socket is not connected.
- WSAENOTSOCK
- The descriptor is not a socket.
See Also
bind(),
socket(),
getsockname().
Description
Get the local name for a socket.
#include <winsock.h>
int PASCAL FAR getsockname(SOCKET s, struct sockaddr FAR *
name, int FAR * namelen);
- s
- A descriptor identifying a bound socket.
- name
- Receives the address (name) of the socket.
- namelen
- The size of the name buffer.
Remarks
getsockname() retrieves the current name for the
specified socket descriptor in name. It is used on a bound and/or
connected socket specified by the s parameter. The local association is
returned. This call is especially useful when a
connect()
call has been made without doing a
bind()
first; this call provides the only means by which you can determine the local
association which has been set by the system.
On return, the namelen argument contains the actual size of the name
returned in bytes.
If a socket was bound to INADDR_ANY, indicating that any of the host's IP
addresses should be used for the socket, getsockname() will not
necessarily return information about the host IP address, unless the socket has
been connected with
connect()
or
accept().
A Windows Sockets application must not assume that the IP address will be
changed from INADDR_ANY unless the socket is connected. This is because for a
multi-homed host the IP address that will be used for the socket is unknown
unless the socket is connected.
Return Value
If no error occurs, getsockname() returns 0.
Otherwise, a value of SOCKET_ERROR is returned, and a specific error code may
be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEFAULT
- The namelen argument is not large enough.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAENOTSOCK
- The descriptor is not a socket.
- WSAEINVAL
- The socket has not been bound to an address with bind().
See Also
bind(),
socket(),
getpeername().
Description
Retrieve a socket option.
#include <winsock.h>
int PASCAL FAR getsockopt ( SOCKET s, int
level, int optname, char FAR *
optval, int FAR * optlen);
- s
- A descriptor identifying a socket.
- level
- The level at which the option is defined; the only supported levels
are SOL_SOCKET and IPPROTO_TCP.
- optname
- The socket option for which the value is to be retrieved.
- optval
- A pointer to the buffer in which the value for the requested option is to
be returned.
- optlen
- A pointer to the size of the optval buffer.
Remarks
getsockopt() retrieves the current value for a socket
option associated with a socket of any type, in any state, and stores the
result in optval. Options may exist at multiple protocol levels, but
they are always present at the uppermost ``socket'' level. Options affect
socket operations, such as whether an operation blocks or not, the routing of
packets, out-of-band data transfer, etc.
The value associated with the selected option is returned in the buffer
optval. The integer pointed to by optlen should originally
contain the size of this buffer; on return, it will be set to the size of the
value returned. For SO_LINGER, this will be the size of a struct linger; for
all other options it will be the size of an integer.
If the option was never set with
setsockopt(),
then getsockopt() returns the default value for the option.
The following options are supported for getsockopt(). The Type
identifies the type of data addressed by optval. The TCP_NODELAY option
uses level IPPROTO_TCP, all other options use level SOL_SOCKET.
Value Type Meaning
--------------- ------------- -----------------------------------------------
SO_ACCEPTCONN BOOL Socket is listen()ing.
SO_BROADCAST BOOL Socket is configured for the transmission of
broadcast messages.
SO_DEBUG BOOL Debugging is enabled.
SO_DONTLINGER BOOL If true, the SO_LINGER option is disabled..
SO_DONTROUTE BOOL Routing is disabled.
SO_ERROR int Retrieve error status and clear.
SO_KEEPALIVE BOOL Keepalives are being sent.
SO_LINGER struct linger Returns the current linger options.
FAR *
SO_OOBINLINE BOOL Out-of-band data is being received in the
normal data stream.
SO_RCVBUF int Buffer size for receives
SO_REUSEADDR BOOL The socket may be bound to an address which
is already in use.
SO_SNDBUF int Buffer size for sends
SO_TYPE int The type of the socket (e.g. SOCK_STREAM).
TCP_NODELAY BOOL Disables the Nagle algorithm for send
coalescing.
BSD options not supported for
getsockopt() are:
Value Type Meaning
--------------- --------------- ------------------------------
SO_RCVLOWAT int Receive low water mark
SO_RCVTIMEO int Receive timeout
SO_SNDLOWAT int Send low water mark
SO_SNDTIMEO int Send timeout
IP_OPTIONS Get options in IP header.
TCP_MAXSEG int Get TCP maximum segment size.
Calling getsockopt() with an unsupported option will result in an error
code of
WSAENOPROTOOPT being returned from
WSAGetLastError().
Return Value
If no error occurs, getsockopt() returns 0.
Otherwise, a value of SOCKET_ERROR is returned, and a specific error code may
be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEFAULT
- The optlen argument was invalid.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAENOPROTOOPT
- The option is unknown or unsupported. In particular, SO_BROADCAST is not
supported on sockets of type SOCK_STREAM, while SO_ACCEPTCON, SO_DONTLINGER,
SO_KEEPALIVE, SO_LINGER and SO_OOBINLINE are not supported on sockets of type
SOCK_DGRAM.
- WSAENOPROTOOPT
- The option is unknown or unsupported. In particular, SO_BROADCAST is not
supported on sockets of type SOCK_STREAM, while SO_ACCEPTCONN, SO_DONTLINGER,
SO_KEEPALIVE, SO_LINGER and SO_OOBINLINE are not supported on sockets of type
SOCK_DGRAM.
- WSAENOTSOCK
- The descriptor is not a socket.
See Also
setsockopt(),
WSAAsyncSelect(),
socket().
Description
Convert a u_long from host to network byte
order.
#include <winsock.h>
u_long PASCAL FAR htonl ( u_long hostlong);
- hostlong
- A 32-bit number in host byte order.
Remarks
This routine takes a 32-bit number in host byte order and
returns a 32-bit number in network byte order.
Return Value
htonl() returns the value in network byte order.
See Also
htons(),
ntohl(),
ntohs().
Description
Convert a u_short from host to network byte
order.
#include <winsock.h>
u_short PASCAL FAR htons ( u_short hostshort );
- hostshort
- A 16-bit number in host byte order.
Remarks
This routine takes a 16-bit number in host byte order and
returns a 16-bit number in network byte order.
Return Value
htons() returns the value in network byte order.
See Also
htonl(),
ntohl(),
ntohs().
Description
Convert a string containing a dotted address into an
in_addr.
#include <winsock.h>
unsigned long PASCAL FAR inet_addr ( const char FAR * cp
);
- cp
- A character string representing a number expressed in the Internet standard ``.'' notation.
Remarks
This function interprets the character string specified by the
cp parameter. This string represents a numeric Internet address
expressed in the Internet standard ``.'' notation. The value returned is a
number suitable for use as an Internet address. All Internet addresses are
returned in network order (bytes ordered from left to right).
Internet Addresses
Values specified using the ``.'' notation take one of the following forms:
When four parts are specified, each is interpreted as a byte of data and
assigned, from left to right, to the four bytes of an Internet address. Note
that when an Internet address is viewed as a 32-bit integer quantity on the
Intel architecture, the bytes referred to above appear as ``d.c.b.a''. That is,
the bytes on an Intel processor are ordered from right to left.
Note: The following notations are only used by Berkeley, and nowhere else on
the Internet. In the interests of compatibility with their software, they are
supported as specified.
When a three part address is specified, the last part is interpreted as a
16-bit quantity and placed in the right most two bytes of the network address.
This makes the three part address format convenient for specifying Class B
network addresses as ``128.net.host''.
When a two part address is specified, the last part is interpreted as a 24-bit
quantity and placed in the right most three bytes of the network address. This
makes the two part address format convenient for specifying Class A network
addresses as ``net.host''.
When only one part is given, the value is stored directly in the network
address without any byte rearrangement.
Return Value
If no error occurs, inet_addr() returns an unsigned
long containing a suitable binary representation of the Internet address given.
If the passed-in string does not contain a legitimate Internet address, for
example if a portion of an ``a.b.c.d'' address exceeds 255, inet_addr()
returns the value INADDR_NONE.
See Also
inet_ntoa().
Description
Convert a network address into a string in dotted
format.
#include <winsock.h>
char FAR * PASCAL FAR inet_ntoa ( struct in_addr in
);
- in
- A structure which represents an Internet host address.
Remarks
This function takes an Internet address structure specified by
the in parameter. It returns an ASCII string representing the address
in ``.'' notation as ``a.b.c.d''. Note that the string returned by
inet_ntoa() resides in memory which is allocated by the Windows Sockets
implementation. The application should not make any assumptions about the way
in which the memory is allocated. The data is guaranteed to be valid until the
next Windows Sockets API call within the same thread, but no longer.
Return Value
If no error occurs, inet_ntoa() returns a char
pointer to a static buffer containing the text address in standard ``.''
notation. Otherwise, it returns NULL. The data should be copied before
another Windows Sockets call is made.
See Also
inet_addr().
Description
Control the mode of a socket.
#include <winsock.h>
int PASCAL FAR ioctlsocket ( SOCKET s, long
cmd, u_long FAR * argp);
- s
- A descriptor identifying a socket.
- cmd
- The command to perform on the socket s.
- argp
- A pointer to a parameter for cmd.
Remarks
This routine may be used on any socket in any state. It is used
to get or retrieve operating parameters associated with the socket, independent
of the protocol and communications subsystem. The following commands are
supported:
- FIONBIO
- Enable or disable non-blocking mode on the socket s. argp
points at an unsigned long, which is non-zero if non-blocking mode is to
be enabled and zero if it is to be disabled. When a socket is created, it
operates in blocking mode (i.e. non-blocking mode is disabled). This is
consistent with BSD sockets.
The WSAAsyncSelect() routine automatically sets
a socket to nonblocking mode. If WSAAsyncSelect() has been issued on a
socket, then any attempt to use ioctlsocket() to set the socket back to
blocking mode will fail with WSAEINVAL.
To set the socket back to blocking
mode, an application must first disable WSAAsyncSelect() by calling
WSAAsyncSelect() with the lEvent parameter equal to 0.
- FIONREAD
- Determine the amount of data which can be read atomically from socket
s. argp points at an unsigned long in which
ioctlsocket() stores the result. If s is of type SOCK_STREAM,
FIONREAD returns the total amount of data which may be read in a single
recv(); this is normally the same as the total amount of data queued on
the socket. If s is of type SOCK_DGRAM, FIONREAD returns the size of
the first datagram queued on the socket.
- SIOCATMARK
- Determine whether or not all out-of-band data has been read. This applies
only to a socket of type SOCK_STREAM which has been configured for in-line
reception of any out-of-band data (SO_OOBINLINE). If no out-of-band data is
waiting to be read, the operation returns TRUE. Otherwise it returns FALSE,
and the next recv() or recvfrom()
performed on the socket will retrieve some or all of the data preceding the
"mark"; the application should use the SIOCATMARK operation to determine
whether any remains. If there is any normal data preceding the "urgent" (out
of band) data, it will be received in order. (Note that a recv() or recvfrom() will never mix
out-of-band and normal data in the same call.) argp points at a
BOOL in which ioctlsocket() stores the result.
Compatibility
This function is a subset of ioctl() as used in
Berkeley sockets. In particular, there is no command which is equivalent to
FIOASYNC, while SIOCATMARK is the only socket-level command which is
supported.
Return Value
Upon successful completion, the ioctlsocket()
returns 0. Otherwise, a value of SOCKET_ERROR is returned, and a specific
error code may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINVAL
- cmd is not a valid command, or argp is not an acceptable
parameter for cmd, or the command is not applicable to the type of
socket supplied
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAENOTSOCK
- The descriptor s is not a socket.
See Also
socket(),
setsockopt(),
getsockopt(),
WSAAsyncSelect().
Description
Establish a socket to listen for incoming
connection.
#include <winsock.h>
int PASCAL FAR listen(SOCKET s, int backlog
);
- s
- A descriptor identifying a bound, unconnected socket.
- backlog
- The maximum length to which the queue of pending connections may grow.
Remarks
To accept connections, a socket is first created with
socket(),
a backlog for incoming connections is specified with listen(), and then
the connections are accepted with
accept().
listen() applies only to sockets that support connections, i.e. those
of type SOCK_STREAM. The socket s is put into ``passive'' mode where
incoming connections are acknowledged and queued pending acceptance by the
process.
This function is typically used by servers that could have more than one
connection request at a time: if a connection request arrives with the queue
full, the client will receive an error with an indication of
WSAECONNREFUSED.
listen() attempts to continue to function rationally when there are no
available descriptors. It will accept connections until the queue is emptied.
If descriptors become available, a later call to listen() or
accept()
will re-fill the queue to the current or most recent ``backlog'', if possible,
and resume listening for incoming connections.
Compatibility
backlog is currently limited (silently) to 5. As
in 4.3BSD, illegal values (less than 1 or greater than 5) are replaced by the
nearest legal value.
Return Value
If no error occurs, listen() returns 0. Otherwise,
a value of SOCKET_ERROR is returned, and a specific error code may be retrieved
by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEADDRINUSE
- An attempt has been made to listen() on an address in use.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEFAULT
- An invalid argument was given.
- WSAEINVAL
- The socket has not been bound with
bind()
or is already connected.
- WSAEISCONN
- The socket is already connected.
- WSAEMFILE
- No more file descriptors are available.
- WSAENOBUFS
- No buffer space is available.
- WSAENOTSOCK
- The descriptor is not a socket.
- WSAEOPNOTSUPP
- The referenced socket is not of a type that supports the listen() operation.
See Also
accept(),
connect(),
socket().
Description
Convert a u_long from network to host byte
order.
#include <winsock.h>
u_long PASCAL FAR ntohl ( u_long netlong);
- netlong
- A 32-bit number in network byte order.
Remarks
This routine takes a 32-bit number in network byte order and
returns a 32-bit number in host byte order.
Return Value
ntohl() returns the value in host byte order.
See Also
htonl(),
htons(),
ntohs().
Description
Convert a u_short from network to host byte
order.
#include <winsock.h>
u_short PASCAL FAR ntohs ( u_short netshort );
- netshort
- A 16-bit number in network byte order.
Remarks
This routine takes a 16-bit number in network byte order and
returns a 16-bit number in host byte order.
Return Value
ntohs() returns the value in host byte order.
See Also
htonl(),
htons(),
ntohl().
Description
Receive data from a socket.
#include <winsock.h>
int PASCAL FAR recv ( int s, char FAR * buf,
int len, int flags);
- s
- A descriptor identifying a connected socket.
- buf
- A buffer for the incoming data.
- len
- The length of buf.
- flags
- Specifies the way in which the call is made.
Remarks
This function is used on connected datagram or stream sockets
specified by the s parameter and is used to read incoming data.
For sockets of type SOCK_STREAM, as much information as is currently available
up to the size of the buffer supplied is returned. If the socket has been
configured for in-line reception of out-of-band data (socket option
SO_OOBINLINE) and out-of-band data is unread, only out-of-band data will be
returned. The application may use the
ioctlsocket()
SIOCATMARK to determine whether any more out-of-band data remains to be read.
For datagram sockets, data is extracted from the first enqueued datagram, up to
the size of the size of the buffer supplied. If the datagram is larger than
the buffer supplied, the excess data is lost, and recv() returns the
error WSAEMSGSIZE.
If no incoming data is available at the socket, the recv() call waits
for data to arrive unless the socket is non-blocking. In this case a value of
SOCKET_ERROR is returned with the error code set to
WSAEWOULDBLOCK. The
select()
or
WSAAsyncSelect()
calls may be used to determine when more data arrives.
If the socket is of type SOCK_STREAM and the remote side has shut down the
connection gracefully, a recv() will complete immediately with 0 bytes
received. If the connection has been abortively disconnected, a recv()
will fail with the error
WSAECONNRESET.
Flags may be used to influence the behavior of the function invocation
beyond the options specified for the associated socket. That is, the semantics
of this function are determined by the socket options and the flags
parameter. The latter is constructed by or-ing any of the following values:
- MSG_PEEK
- Peek at the incoming data. The data is copied into the buffer but is not
removed from the input queue.
- MSG_OOB
- Process out-of-band data (See Out of Band
Data for a discussion of this topic.)
Return Value
If no error occurs, recv() returns the number of
bytes received. If the connection has been closed, it returns 0. Otherwise, a
value of SOCKET_ERROR is returned, and a specific error code may be retrieved
by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAENOTCONN
- The socket is not connected.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAENOTSOCK
- The descriptor is not a socket.
- WSAEOPNOTSUPP
- MSG_OOB was specified, but the socket is not of type SOCK_STREAM.
- WSAESHUTDOWN
- The socket has been shutdown; it is not possible to recv() on a
socket after
shutdown()
has been invoked with how set to 0 or 2.
- WSAEWOULDBLOCK
- The socket is marked as non-blocking and the receive operation would block.
- WSAEMSGSIZE
- The datagram was too large to fit into the specified buffer and was
truncated.
- WSAEINVAL
- The socket has not been bound with bind().
- WSAECONNABORTED
- The virtual circuit was aborted due to timeout or other failure.
- WSAECONNRESET
- The virtual circuit was reset by the remote side.
See Also
recvfrom(),
send(),
select(),
WSAAsyncSelect(),
socket().
Description
Receive a datagram and store the source address.
#include <winsock.h>
int PASCAL FAR recvfrom ( int s, char FAR *
buf, int len, int flags, struct
sockaddr FAR * from, int FAR * fromlen
);
- s
- A descriptor identifying a bound socket.
- buf
- A buffer for the incoming data.
- len
- The length of buf.
- flags
- Specifies the way in which the call is made.
- from
- An optional pointer to a buffer which will hold the source address upon
return.
- fromlen
- An optional pointer to the size of the from buffer.
Remarks
This function is used to read incoming data on a (possibly
connected) socket and capture the address from which the data was sent.
For sockets of type SOCK_STREAM, as much information as is currently available
up to the size of the buffer supplied is returned. If the socket has been
configured for in-line reception of out-of-band data (socket option
SO_OOBINLINE) and out-of-band data is unread, only out-of-band data will be
returned. The application may use the
ioctlsocket()
SIOCATMARK to determine whether any more out-of-band data remains to be read.
The from and fromlen parameters are ignored for SOCK_STREAM
sockets.
For datagram sockets, data is extracted from the first enqueued datagram, up to
the size of the size of the buffer supplied. If the datagram is larger than
the buffer supplied, the buffer is filled with the first part of the message,
the excess data is lost, and recvfrom() returns the error code
WSAEMSGSIZE.
If from is non-zero, and the socket is of type SOCK_DGRAM, the network
address of the peer which sent the data is copied to the corresponding struct
sockaddr. The value pointed to by fromlen is initialized to the size of
this structure, and is modified on return to indicate the actual size of the
address stored there.
If no incoming data is available at the socket, the recvfrom() call
waits for data to arrive unless the socket is non-blocking. In this case a
value of SOCKET_ERROR is returned with the error code set to
WSAEWOULDBLOCK.
The
select()
or
WSAAsyncSelect()
calls may be used to determine when more data arrives.
If the socket is of type SOCK_STREAM and the remote side has shut down the
connection gracefully, a recvfrom() will complete immediately with 0
bytes received. If the connection has been abortively disconnected, a
recvfrom() will fail with the error
WSAECONNRESET.
Flags may be used to influence the behavior of the function invocation
beyond the options specified for the associated socket. That is, the semantics
of this function are determined by the socket options and the flags
parameter. The latter is constructed by or-ing any of the following values:
- MSG_PEEK
- Peek at the incoming data. The data is copied into the buffer but is not
removed from the input queue.
- MSG_OOB
- Process out-of-band data (See
Out
of Band Data for a discussion of this topic.)
Return Value
If no error occurs, recvfrom() returns the number of
bytes received. If the connection has been closed, it returns 0. Otherwise, a
value of SOCKET_ERROR is returned, and a specific error code may be retrieved
by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEFAULT
- The fromlen argument was invalid: the from buffer was too
small to accommodate the peer address.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEINVAL
- The socket has not been bound with
bind().
- WSAENOTCONN
- The socket is not connected (SOCK_STREAM only).
- WSAENOTSOCK
- The descriptor is not a socket.
- WSAEOPNOTSUPP
- MSG_OOB was specified, but the socket is not of type SOCK_STREAM.
- WSAESHUTDOWN
- The socket has been shutdown; it is not possible to recvfrom() on a
socket after
shutdown()
has been invoked with how set to 0 or 2.
- WSAEWOULDBLOCK
- The socket is marked as non-blocking and the recvfrom() operation
would block.
- WSAEMSGSIZE
- The datagram was too large to fit into the specified buffer and was
truncated.
- WSAECONNABORTED
- The virtual circuit was aborted due to timeout or other failure.
- WSCONNRESET
- The virtual circuit was reset by the remote side.
See Also
recv(),
send(),
socket(),
WSAAsyncSelect().
Description
Determine the status of one or more sockets, waiting if
necessary.
#include <winsock.h>
long PASCAL FAR select ( int nfds, fd_set FAR *
readfds, fd_set FAR * writefds, fd_set FAR *
exceptfds, const struct timeval FAR * timeout
);
- nfds
- This argument is ignored and included only for the sake of compatibility.
- readfds
- An optional pointer to a set of sockets to be checked for readability.
- writefds
- An optional pointer to a set of sockets to be checked for writeability
- exceptfds
- An optional pointer to a set of sockets to be checked for errors.
- timeout
- The maximum time for select() to wait, or NULL for blocking operation.
Remarks
This function is used to determine the status of one or more
sockets. For each socket, the caller may request information on read, write or
error status. The set of sockets for which a given status is requested is
indicated by an fd_set structure. Upon return, the structure is updated to
reflect the subset of these sockets which meet the specified condition, and
select() returns the number of sockets meeting the conditions. A set of
macros is provided for manipulating an fd_set. These macros are compatible
with those used in the Berkeley software, but the underlying representation is
completely different.
The parameter readfds identifies those sockets which are to be checked
for readability. If the socket is currently
listen()ing,
it will be marked as readable if an incoming connection request has been
received, so that an
accept()
is guaranteed to complete without blocking. For other sockets, readability
means that queued data is available for reading or, for sockets of type
SOCK_STREAM, that the virtual socket corresponding to the socket has been
closed, so that a
recv()
or
recvfrom()
is guaranteed to complete without blocking. If the virtual circuit was closed
gracefully, then a
recv()
will return immediately with 0 bytes read; if the virtual circuit was
closed abortively, then a
recv()
will complete immediately with the error code
WSAECONNRESET. The presence
of out-of-band data will be checked if the socket option SO_OOBINLINE has been
enabled (see
setsockopt()).
The parameter writefds identifies those sockets which are to be checked
for writeability. If a socket is
connect()ing
(non-blocking), writeability means that the connection establishment is
complete. For other sockets, writeability means that a
send()
or
sendto()
will complete without blocking. [It is not specified how long this guarantee
can be assumed to be valid, particularly in a multithreaded environment.]
The parameter exceptfds identifies those sockets which are to be checked
for the presence of out-of-band data or any exceptional error conditions. Note
that out-of-band data will only be reported in this way if the option
SO_OOBINLINE is FALSE. For a SOCK_STREAM, the breaking of the connection by
the peer or due to KEEPALIVE failure will be indicated as an exception. This
specification does not define which other errors will be included. If a socket
is connect()ing (non-blocking), failure of the connect attempt is
indicated in exceptfds.
Any of readfds, writefds, or exceptfds may be given as
NULL if no descriptors are of interest.
Four macros are defined in the header file winsock.h for manipulating
the descriptor sets. The variable FD_SETSIZE determines the maximum number of
descriptors in a set. (The default value of FD_SETSIZE is 64, which may be
modified by #defining FD_SETSIZE to another value before #including
winsock.h.) Internally, an fd_set is represented as an array of
SOCKETs; the last valid entry is followed by an element set to INVALID_SOCKET.
The macros are:
- FD_CLR(s, *set)
- Removes the descriptor s from set.
- FD_ISSET(s, *set)
- Nonzero if s is a member of the set, zero otherwise.
- FD_SET(s, *set)
- Adds descriptor s to set.
- FD_ZERO(*set)
- Initializes the set to the NULL set.
The parameter timeout controls how long the select() may
take to complete. If timeout is a null pointer, select() will
block indefinitely until at least one descriptor meets the specified criteria.
Otherwise, timeout points to a struct timeval which specifies the
maximum time that select() should wait before returning. If the timeval
is initialized to {0, 0}, select() will return immediately; this is used
to "poll" the state of the selected sockets. If this is the case, then the
select() call is considered nonblocking and the standard assumptions for
nonblocking calls apply. For example, the blocking hook must not be called,
and the Windows Sockets implementation must not yield.
Return Value
select() returns the total number of descriptors
which are ready and contained in the fd_set structures, or 0 if the time limit
expired, or SOCKET_ERROR if an error occurred. If the return value is
SOCKET_ERROR,
WSAGetLastError()
may be used to retrieve a specific error code.
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINVAL
- The timeout value is not valid.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAENOTSOCK
- One of the descriptor sets contains an entry which is not a socket.
See Also
WSAAsyncSelect(),
accept(),
connect(),
recv(),
recvfrom(),
send().
Description
Send data on a connected socket.
#include <winsock.h>
int PASCAL FAR send ( SOCKET s, const char FAR *
buf, int len, int flags
);
- s
- A descriptor identifying a connected socket.
- buf
- A buffer containing the data to be transmitted.
- len
- The length of the data in buf.
- flags
- Specifies the way in which the call is made.
Remarks
send() is used on connected datagram or stream sockets
and is used to write outgoing data on a socket. For datagram sockets, care
must be taken not to exceed the maximum IP packet size of the underlying
subnets, which is given by the iMaxUdpDg element in the WSAData
structure returned by
WSAStartup().
If the data is too long to pass atomically through the underlying protocol the
error WSAEMSGSIZE
is returned, and no data is transmitted.
Note that the successful completion of a send() does not indicate that
the data was successfully delivered.
If no buffer space is available within the transport system to hold the data to
be transmitted, send() will block unless the socket has been placed in a
non-blocking I/O mode. On non-blocking SOCK_STREAM sockets, the number of
bytes written may be between 1 and the requested length, depending on buffer
availability on both the local and foreign hosts. The
select()
call may be used to determine when it is possible to send more data.
Flags may be used to influence the behavior of the function invocation
beyond the options specified for the associated socket. That is, the semantics
of this function are determined by the socket options and the flags
parameter. The latter is constructed by or-ing any of the following values:
- MSG_DONTROUTE
- Specifies that the data should not be subject to routing. A Windows
Sockets supplier may choose to ignore this flag; see also the discussion of the
SO_DONTROUTE option in Socket Options.
- MSG_OOB
- Send out-of-band data (SOCK_STREAM only; see also Out of Band Data)
Return Value
If no error occurs, send() returns the total number
of characters sent. (Note that this may be less than the number indicated by
len.) Otherwise, a value of SOCKET_ERROR is returned, and a specific
error code may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEACCES
- The requested address is a broadcast address, but the appropriate flag was
not set.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEFAULT
- The buf is not in a valid part of the user address space.
- WSAENETRESET
- The connection must be reset because the Windows Sockets implementation
dropped it.
- WSAENOBUFS
- The Windows Sockets implementation reports a buffer deadlock.
- WSAENOTCONN
- The socket is not connected.
- WSAENOTSOCK
- The descriptor is not a socket.
- WSAEOPNOTSUPP
- MSG_OOB was specified, but the socket is not of type SOCK_STREAM.
- WSAESHUTDOWN
- The socket has been shutdown; it is not possible to send() on a
socket after
shutdown()
has been invoked with how set to 1 or 2.
- WSAEWOULDBLOCK
- The socket is marked as non-blocking and the requested operation would
block.
- WSAEMSGSIZE
- The socket is of type SOCK_DGRAM, and the datagram is larger than the
maximum supported by the Windows Sockets implementation.
- WSAEINVAL
- The socket has not been bound with
bind().
- WSAECONNABORTED
- The virtual circuit was aborted due to timeout or other failure.
- WSAECONNRESET
- The virtual circuit was reset by the remote side.
See Also
recv(),
recvfrom(),
socket(),
sendto(),
WSAStartup().
Description
Send data to a specific destination.
#include <winsock.h>
int PASCAL FAR sendto ( SOCKET s, const char FAR *
buf, int len, int flags, const struct
sockaddr FAR * to, int tolen);
- s
- A descriptor identifying a socket.
- buf
- A buffer containing the data to be transmitted.
- len
- The length of the data in buf.
- flags
- Specifies the way in which the call is made.
- to
- A optional pointer to the address of the target socket.
- tolen
- The size of the address in to.
Remarks
sendto() is used on datagram or stream sockets and is
used to write outgoing data on a socket. For datagram sockets, care must be
taken not to exceed the maximum IP packet size of the underlying subnets, which
is given by the iMaxUdpDg element in the WSAData structure returned by
WSAStartup().
If the data is too long to pass atomically through the underlying protocol the
error WSAEMSGSIZE
is returned, and no data is transmitted.
Note that the successful completion of a sendto() does not indicate that
the data was successfully delivered.
sendto() is normally used on a SOCK_DGRAM socket to send a datagram to a
specific peer socket identified by the to parameter. On a SOCK_STREAM
socket, the to and tolen parameters are ignored; in this case the
sendto() is equivalent to
send().
To send a broadcast (on a SOCK_DGRAM only), the address in the to
parameter should be constructed using the special IP address INADDR_BROADCAST
(defined in winsock.h) together with the intended port number. It is
generally inadvisable for a broadcast datagram to exceed the size at which
fragmentation may occur, which implies that the data portion of the datagram
(excluding headers) should not exceed 512 bytes.
If no buffer space is available within the transport system to hold the data to
be transmitted, sendto() will block unless the socket has been placed in
a non-blocking I/O mode. On non-blocking SOCK_STREAM sockets, the number of
bytes written may be between 1 and the requested length, depending on buffer
availability on both the local and foreign hosts. The
select()
call may be used to determine when it is possible to send more data.
Flags may be used to influence the behavior of the function invocation
beyond the options specified for the associated socket. That is, the semantics
of this function are determined by the socket options and the flags
parameter. The latter is constructed by or-ing any of the following values:
- MSG_DONTROUTE
- Specifies that the data should not be subject to routing. A Windows
Sockets supplier may choose to ignore this flag; see also the discussion of the
SO_DONTROUTE option in Socket Options.
- MSG_OOB
- Send out-of-band data (SOCK_STREAM only; see also Out of Band Data)
Return Value
If no error occurs, sendto() returns the total
number of characters sent. (Note that this may be less than the number
indicated by len.) Otherwise, a value of SOCKET_ERROR is returned, and a
specific error code may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEACCES
- The requested address is a broadcast address, but the appropriate flag was
not set.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEFAULT
- The buf or to are not in a valid part of the user address
space, or the to argument is too small (less than the sizeof a struct sockaddr).
- WSAENETRESET
- The connection must be reset because the Windows Sockets implementation
dropped it.
- WSAENOBUFS
- The Windows Sockets implementation reports a buffer deadlock.
- WSAENOTCONN
- The socket is not connected (SOCK_STREAM only).
- WSAENOTSOCK
- The descriptor is not a socket.
- WSAEOPNOTSUPP
- MSG_OOB was specified, but the socket is not of type SOCK_STREAM.
- WSAESHUTDOWN
- The socket has been shutdown; it is not possible to sendto() on a
socket after
shutdown()
has been invoked with how set to 1 or 2.
- WSAEWOULDBLOCK
- The socket is marked as non-blocking and the requested operation would
block.
- WSAEMSGSIZE
- The socket is of type SOCK_DGRAM, and the datagram is larger than the
maximum supported by the Windows Sockets implementation.
- WSAECONNABORTED
- The virtual circuit was aborted due to timeout or other failure.
- WSAECONNRESET
- The virtual circuit was reset by the remote side.
- WSAEADDRNOTAVAIL
- The specified address is not available from the local machine.
- WSAEAFNOSUPPORT
- Addresses in the specified family cannot be used with this socket.
- WSAEDESTADDRREQ
- A destination address is required.
- WSAENETUNREACH
- The network can't be reached from this host at this time.
See Also
recv(),
recvfrom(),
socket(),
send(),
WSAStartup().
Description
Set a socket option.
#include <winsock.h>
int PASCAL FAR setsockopt ( SOCKET s, int
level, int optname, const char FAR *
optval, int optlen);
- s
- A descriptor identifying a socket.
- level
- The level at which the option is defined; the only supported levels
are SOL_SOCKET and IPPROTO_TCP.
- optname
- The socket option for which the value is to be set.
- optval
- A pointer to the buffer in which the value for the requested option is
supplied.
- optlen
- The size of the optval buffer.
Remarks
setsockopt() sets the current value for a socket option
associated with a socket of any type, in any state. Although options may exist
at multiple protocol levels, this specification only defines options that exist
at the uppermost ``socket'' level. Options affect socket operations, such as
whether expedited data is received in the normal data stream, whether broadcast
messages may be sent on the socket, etc.
There are two types of socket options: Boolean options that enable or disable a
feature or behavior, and options which require an integer value or structure.
To enable a Boolean option, optval points to a nonzero integer. To
disable the option optval points to an integer equal to zero.
optlen should be equal to sizeof(int) for Boolean options. For other
options, optval points to the an integer or structure that contains the
desired value for the option, and optlen is the length of the integer or
structure.
SO_LINGER controls the action taken when unsent data is queued on a socket and a
closesocket()
is performed. See
closesocket()
for a description of the way in which the SO_LINGER settings affect the
semantics of
closesocket().
The application sets the desired behavior by creating a struct linger
(pointed to by the optval argument) with the following elements:
struct linger {
int l_onoff;
int l_linger;
}
To enable SO_LINGER, the application should set l_onoff to a non-zero
value, set l_linger to 0 or the desired timeout (in seconds), and call
setsockopt(). To enable SO_DONTLINGER (i.e. disable SO_LINGER)
l_onoff should be set to zero and setsockopt() should be
called.
By default, a socket may not be bound (see
bind())
to a local address which is already in use. On occasions, however, it may be
desirable to "re-use" an address in this way. Since every connection is
uniquely identified by the combination of local and remote addresses, there is
no problem with having two sockets bound to the same local address as long as
the remote addresses are different. To inform the Windows Sockets
implementation that a
bind()
on a socket should not be disallowed because the desired address is already in
use by another socket, the application should set the SO_REUSEADDR socket
option for the socket before issuing the
bind().
Note that the option is interpreted only at the time of the
bind():
it is therefore unnecessary (but harmless) to set the option on a socket which
is not to be bound to an existing address, and setting or resetting the option
after the
bind()
has no effect on this or any other socket..
An application may request that the Windows Sockets implementation enable the
use of "keep-alive" packets on TCP connections by turning on the SO_KEEPALIVE
socket option. A Windows Sockets implementation need not support the use of
keep-alives: if it does, the precise semantics are implementation-specific but
should conform to section 4.2.3.6 of RFC 1122: Requirements for Internet
Hosts -- Communication Layers. If a connection is dropped as the result of
"keep-alives" the error code
WSAENETRESET
is returned to any calls in progress
on the socket, and any subsequent calls will fail with
WSAENOTCONN.
The TCP_NODELAY option disables the Nagle algorithm. The Nagle algorithm is
used to reduce the number of small packets sent by a host by buffering
unacknowledged send data until a full-size packet can be sent. However, for
some applications this algorithm can impede performance, and TCP_NODELAY may be
used to turn it off. Application writers should not set TCP_NODELAY unless the
impact of doing so is well-understood and desired, since setting TCP_NODELAY
can have a significant negative impact of network performance. TCP_NODELAY is
the only supported socket option which uses level IPPROTO_TCP; all other
options use level SOL_SOCKET.
Windows Sockets suppliers are encouraged (but not required) to supply output
debug information if the SO_DEBUG option is set by an application. The
mechanism for generating the debug information and the form it takes are beyond
the scope of this specification.
The following options are supported for setsockopt(). The Type
identifies the type of data addressed by optval.
Value Type Meaning
--------------- --------------- -----------------------------------------------
SO_BROADCAST BOOL Allow transmission of broadcast messages on the
socket.
SO_DEBUG BOOL Record debugging information.
SO_DONTLINGER BOOL Don't block close waiting for unsent data to be
sent. Setting this option is equivalent to
setting SO_LINGER with l_onoff set to
zero.
SO_DONTROUTE BOOL Don't route: send directly to interface.
SO_KEEPALIVE BOOL Send keepalives
SO_LINGER struct linger Linger on close if unsent data is present
FAR *
SO_OOBINLINE BOOL Receive out-of-band data in the normal data
stream.
SO_RCVBUF int Specify buffer size for receives
SO_REUSEADDR BOOL Allow the socket to be bound to an address
which is already in use. (See bind().)
SO_SNDBUF int Specify buffer size for sends
TCP_NODELAY BOOL Disables the Nagle algorithm for send
coalascing.
BSD options not supported for setsockopt() are:
Value Type Meaning
--------------- --------------- --------------------------
SO_ACCEPTCON BOOL Socket is listening
SO_ERROR int Get error status and clear
SO_RCVLOWAT int Receive low water mark
SO_RCVTIMEO int Receive timeout
SO_SNDLOWAT int Send low water mark
SO_SNDTIMEO int Send timeout
SO_TYPE int Type of the socket
IP_OPTIONS Set options field in IP header.
Return Value
If no error occurs, setsockopt() returns 0.
Otherwise, a value of SOCKET_ERROR is returned, and a specific error code may
be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEFAULT
- optval is not in a valid part of the process address space.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEINVAL
- level is not valid, or the information in optval is not valid.
- WSAENETRESET
- Connection has timed out when SO_KEEPALIVE is set.
- WSAENOPROTOOPT
- The option is unknown or unsupported. In particular, SO_BROADCAST is not
supported on sockets of type SOCK_STREAM, while SO_DONTLINGER, SO_KEEPALIVE,
SO_LINGER and SO_OOBINLINE are not supported on sockets of type SOCK_DGRAM.
- WSAENOTCONN
- Connection has been reset when SO_KEEPALIVE is set.
- WSAENOTSOCK
- The descriptor is not a socket.
See Also
bind(),
getsockopt(),
ioctlsocket(),
socket(),
WSAAsyncSelect().
Description
Disable sends and/or receives on a socket.
#include <winsock.h>
int PASCAL FAR shutdown ( SOCKET s, int how
);
- s
- A descriptor identifying a socket.
- how
- A flag that describes what types of operation will no longer be allowed.
Remarks
shutdown() is used on all types of sockets to disable
reception, transmission, or both.
If how is 0, subsequent receives on the socket will be disallowed. This
has no effect on the lower protocol layers. For TCP, the TCP window is not
changed and incoming data will be accepted (but not acknowledged) until the
window is exhausted. For UDP, incoming datagrams are accepted and queued. In
no case will an ICMP error packet be generated.
If how is 1, subsequent sends are disallowed. For TCP sockets, a FIN
will be sent.
Setting how to 2 disables both sends and receives as described above.
Note that shutdown() does not close the socket, and resources attached
to the socket will not be freed until
closesocket()
is invoked.
Comments
shutdown() does not block regardless of the SO_LINGER
setting on the socket.
An application should not rely on being able to re-use a socket after it has
been shut down. In particular, a Windows Sockets implementation is not
required to support the use of
connect()
on such a socket.
Return Value
If no error occurs, shutdown() returns 0.
Otherwise, a value of SOCKET_ERROR is returned, and a specific error code may
be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINVAL
- how is not valid.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAENOTCONN
- The socket is not connected (SOCK_STREAM only).
- WSAENOTSOCK
- The descriptor is not a socket.
See Also
connect(),
socket().
Description
Create a socket.
#include <winsock.h>
SOCKET PASCAL FAR socket ( int af, int type,
int protocol);
- af
- An address format specification. The only format currently supported is
PF_INET, which is the ARPA Internet address format.
- type
- A type specification for the new socket.
- protocol
- A particular protocol to be used with the socket, or 0 if the caller does
not wish to specify a protocol.
Remarks
socket() allocates a socket descriptor of the specified
address family, data type and protocol, as well as related resources. If a
protocol is not specified (i.e. equal to 0), the default for the specified
connection mode is used.
Only a single protocol exists to support a particular socket type using a given
address format. However, the address family may be given as AF_UNSPEC
(unspecified), in which case the protocol parameter must be specified.
The protocol number to use is particular to the ``communication domain'' in
which communication is to take place.
The following type specifications are supported:
- SOCK_STREAM
- Provides sequenced, reliable, two-way, connection-based byte streams with
an out-of-band data transmission mechanism. Uses TCP for the Internet address
family.
- SOCK_DGRAM
- Supports datagrams, which are connectionless, unreliable buffers of a
fixed (typically small) maximum length. Uses UDP for the Internet address
family.
Sockets of type SOCK_STREAM are full-duplex byte streams. A stream socket must
be in a connected state before any data may be sent or received on it. A
connection to another socket is created with a
connect()
call. Once connected, data may be transferred using
send()
and
recv()
calls. When a session has been completed, a
closesocket()
must be performed. Out-of-band data may also be transmitted as described in
send()
and received as described in
recv().
The communications protocols used to implement a SOCK_STREAM ensure that data
is not lost or duplicated. If data for which the peer protocol has buffer
space cannot be successfully transmitted within a reasonable length of time,
the connection is considered broken and subsequent calls will fail with the
error code set to WSAETIMEDOUT.
SOCK_DGRAM sockets allow sending and receiving of datagrams to and from
arbitrary peers using
sendto()
and
recvfrom().
If such a socket is
connect()ed
to a specific peer, datagrams may be send to that peer
send()
and may be received from (only) this peer using
recv().
Return Value
If no error occurs, socket() returns a descriptor
referencing the new socket. Otherwise, a value of INVALID_SOCKET is returned,
and a specific error code may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEAFNOSUPPORT
- The specified address family is not supported..
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEMFILE
- No more file descriptors are available.
- WSAENOBUFS
- No buffer space is available. The socket cannot be created.
- WSAEPROTONOSUPPORT
- The specified protocol is not supported.
- WSAEPROTOTYPE
- The specified protocol is the wrong type for this socket.
- WSAESOCKTNOSUPPORT
- The specified socket type is not supported in this address family.
See Also
accept(),
bind(),
connect(),
getsockname(),
getsockopt(),
setsockopt(),
listen(),
recv(),
recvfrom(),
select(),
send(),
sendto(),
shutdown(),
ioctlsocket().
gethostbyaddr()
gethostbyname()
gethostname()
getprotobyname()
getprotobynumber()
getservbyname()
getservbyport()
Description
Get host information corresponding to an address.
#include <winsock.h>
struct hostent FAR * PASCAL FAR gethostbyaddr ( const char FAR *
addr, int len, int type
);
- addr
- A pointer to an address in network byte order.
- len
- The length of the address, which must be 4 for PF_INET addresses.
- type
- The type of the address, which must be PF_INET.
Remarks
gethostbyaddr() returns a pointer to the following
structure which contains the name(s) and address which correspond to the given
address.
struct hostent {
char FAR * h_name;
char FAR * FAR *h_aliases;
short h_addrtype;
short h_length;
char FAR * FAR *h_addr_list;
};
The members of this structure are:
- h_name
- Official name of the host (PC).
- h_aliases
- A NULL -terminated array of alternate names.
- h_addrtype
- The type of address being returned; for Windows Sockets this is always
PF_INET.
- h_length
- The length, in bytes, of each address; for PF_INET, this is always 4.
- h_addr_list
- A NULL-terminated list of addresses for the host. Addresses are returned
in network byte order.
The macro h_addr is defined to be h_addr_list[0] for compatibility with older
software.
The pointer which is returned points to a structure which is allocated by the
Windows Sockets implementation. The application must never attempt to modify
this structure or to free any of its components. Furthermore, only one copy of
this structure is allocated per thread, and so the application should copy any
information which it needs before issuing any other Windows Sockets API
calls.
Return Value
If no error occurs, gethostbyaddr() returns a
pointer to the hostent structure described above. Otherwise it returns a NULL
pointer and a specific error number may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAHOST_NOT_FOUND
- Authoritative Answer Host not found.
- WSATRY_AGAIN
- Non-Authoritative Host not found, or SERVERFAIL.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
See Also
WSAAsyncGetHostByAddr(),
gethostbyname(),
Description
Get host information corresponding to a hostname.
#include <winsock.h>
struct hostent FAR * PASCAL FAR gethostbyname ( const char FAR *
name);
- name
- A pointer to the name of the host.
Remarks
gethostbyname() returns a pointer to a hostent structure
as described under
gethostbyaddr().
The contents of this structure correspond to the hostname name.
The pointer which is returned points to a structure which is allocated by the
Windows Sockets implementation. The application must never attempt to modify
this structure or to free any of its components. Furthermore, only one copy of
this structure is allocated per thread, and so the application should copy any
information which it needs before issuing any other Windows Sockets API
calls.
A gethostbyname() implementation must not resolve IP address strings
passed to it. Such a request should be treated exactly as if an unknown host
name were passed. An application with an IP address string to resolve should
use
inet_addr()
to convert the string to an IP address, then
gethostbyaddr()
to obtain the hostent structure.
Return Value
If no error occurs, gethostbyname() returns a
pointer to the hostent structure described above. Otherwise it returns a NULL
pointer and a specific error number may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAHOST_NOT_FOUND
- Authoritative Answer Host not found.
- WSATRY_AGAIN
- Non-Authoritative Host not found, or SERVERFAIL.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
See Also
WSAAsyncGetHostByName(),
gethostbyaddr()
Description
Return the standard host name for the local
machine.
#include <winsock.h>
int PASCAL FAR gethostname ( char FAR * name, int
namelen );
- name
- A pointer to a buffer that will receive the host name.
- namelen
- The length of the buffer.
Remarks
This routine returns the name of the local host into
the buffer specified by the name parameter. The host name is returned
as a null-terminated string. The form of the host name is dependent on the
Windows Sockets implementation--it may be a simple host name, or it may be a
fully qualified domain name. However, it is guaranteed that the name returned
will be successfully parsed by gethostbyname() and
WSAAsyncGetHostByName().
Return Value
If no error occurs, gethostname() reutrns 0,
otherwise it returns SOCKET_ERROR and a specific error code may be retrieved by
calling
WSAGetLastError().
Error Codes
- WSAEFAULT
- The namelen parameter is too small
- WSAENOTINITIALISED
- A successful WSAStartup() must occur before using
this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the
network subsystem has failed.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
See Also
gethostbyname(),
WSAAsyncGetHostByName().
Description
Get protocol information corresponding to a protocol
name.
#include <winsock.h>
struct protoent FAR * PASCAL FAR getprotobyname ( const char FAR *
name);
- name
- A pointer to a protocol name.
Remarks
getprotobyname() returns a pointer to the following
structure which contains the name(s) and protocol number which correspond to
the given protocol name.
struct protoent {
char FAR * p_name;
char FAR * FAR *p_aliases;
short p_proto;
};
The members of this structure are:
- p_name
- Official name of the protocol.
- p_aliases
- A NULL-terminated array of alternate names.
- p_proto
- The protocol number, in host byte order.
The pointer which is returned points to a structure which is allocated by the
Windows Sockets library. The application must never attempt to modify this
structure or to free any of its components. Furthermore only one copy of this
structure is allocated per thread, and so the application should copy any
information which it needs before issuing any other Windows Sockets API calls.
Return Value
If no error occurs, getprotobyname() returns a
pointer to the protoent structure described above. Otherwise it returns a NULL
pointer and a specific error number may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
See Also
WSAAsyncGetProtoByName(),
getprotobynumber().
Description
Get protocol information corresponding to a protocol
number.
#include <winsock.h>
struct protoent FAR * PASCAL FAR getprotobynumber ( int number
);
- number
- A protocol number, in host byte order.
Remarks
This function returns a pointer to a protoent structure as
described above in getprotobyname(). The contents of the structure
correspond to the given protocol number.
The pointer which is returned points to a structure which is allocated by the
Windows Sockets implementation. The application must never attempt to modify
this structure or to free any of its components. Furthermore, only one copy of
this structure is allocated per thread, and so the application should copy any
information which it needs before issuing any other Windows Sockets API calls.
Return Value
If no error occurs, getprotobynumber() returns a
pointer to the protoent structure described above. Otherwise it returns a NULL
pointer and a specific error number may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
See Also
WSAAsyncGetProtoByNumber(),
getprotobyname()
Description
Get service information corresponding to a service name and
protocol.
#include <winsock.h>
struct servent FAR * PASCAL FAR getservbyname ( const char FAR *
name, const char FAR * proto);
- name
- A pointer to a service name.
- proto
- An optional pointer to a protocol name. If this is NULL,
getservbyname() returns the first service entry for which the
name matches the s_name or one of the s_aliases. Otherwise
getservbyname() matches both the name and the proto.
Remarks
getservbyname() returns a pointer to the following
structure which contains the name(s) and service number which correspond to the
given service name.
struct servent {
char FAR * s_name;
char FAR * FAR *s_aliases;
short s_port;
char FAR * s_proto;
};
The members of this structure are:
- s_name
- Official name of the service.
- s_aliases
- A NULL-terminated array of alternate names.
- s_port
- The port number at which the service may be contacted. Port numbers are
in network byte order.
- s_proto
- The name of the protocol to use when contacting the service.
The pointer which is returned points to a structure which is allocated by the
Windows Sockets library. The application must never attempt to modify this
structure or to free any of its components. Furthermore only one copy of this
structure is allocated per thread, and so the application should copy any
information which it needs before issuing any other Windows Sockets API calls.
Return Value
If no error occurs, getservbyname() returns a
pointer to the servent structure described above. Otherwise it returns a NULL
pointer and a specific error number may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful WSAStartup() must occur before using
this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEINTR
- The (blocking) call was canceled via
WSACancelBlockingCall()
See Also
WSAAsyncGetServByName(),
getservbyport()
Description
Get service information corresponding to a port and
protocol.
#include <winsock.h>
struct servent FAR * PASCAL FAR getservbyport ( int port,
const char FAR * proto);
- port
- The port for a service, in network byte order.
- proto
- An optional pointer to a protocol name. If this is NULL,
getservbyport() returns the first service entry for which the port
matches the s_port. Otherwise getservbyport() matches both the
port and the proto.
Remarks
getservbyport() returns a pointer a servent structure as
described above for
getservbyname().
The pointer which is returned points to a structure which is allocated by the
Windows Sockets implementation. The application must never attempt to modify
this structure or to free any of its components. Furthermore, only one copy of
this structure is allocated per thread, and so the application should copy any
information which it needs before issuing any other Windows Sockets API calls.
Return Value
If no error occurs, getservbyport() returns a
pointer to the servent structure described above. Otherwise it returns a NULL
pointer and a specific error number may be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEINTR
- The (blocking) call was canceled via WSACancelBlockingCall()
See Also
WSAAsyncGetServByPort(),
getservbyname()
WSAAsyncGetHostByAddr()
WSAAsyncGetHostByName()
WSAAsyncGetProtoByName()
WSAAsyncGetProtoByNumber()
WSAAsyncGetServByName()
WSAAsyncGetServByPort()
WSAAsyncSelect()
WSACancelAsyncRequest()
WSACancelBlockingCall()
WSACleanup()
WSAGetLastError()
WSAIsBlocking()
WSASetBlockingHook()
WSASetLastError()
WSAStartup()
WSAUnhookBlockingHook()
Description
Get host information corresponding to an address -
asynchronous version.
#include <winsock.h>
HANDLE PASCAL FAR WSAAsyncGetHostByAddr ( HWND hWnd, unsigned
int wMsg, const char FAR * addr, int
len, int type, char FAR * buf, int
buflen);
- hWnd
- The handle of the window which should receive a message when the
asynchronous request completes.
- wMsg
- The message to be received when the asynchronous request completes.
- addr
- Apointer to the network address for the host. Host addresses are
stored in network byte order.
- len
- The length of the address, which must be 4 for PF_INET.
- type
- The type of the address, which must be PF_INET.
- buf
- A pointer to the data area to receive the hostent data. Note that this
must be larger than the size of a hostent structure. This is because the data
area supplied is used by the Windows Sockets implementation to contain not only
a hostent structure but any and all of the data which is referenced by members
of the hostent structure. It is recommended that you supply a buffer of
MAXGETHOSTSTRUCT bytes.
- buflen
- The size of data area buf above.
Remarks
This function is an asynchronous version of
gethostbyaddr(),
and is used to retrieve host name and address information corresponding to a
network address. The Windows Sockets implementation initiates the operation
and returns to the caller immediately, passing back an asynchronous task
handle which the application may use to identify the operation. When the
operation is completed, the results (if any) are copied into the buffer
provided by the caller and a message is sent to the application's window.
When the asynchronous operation is complete the application's window
hWnd receives message wMsg. The wParam argument contains
the asynchronous task handle as returned by the original function call. The
high 16 bits of lParam contain any error code. The error code may be
any error as defined in winsock.h. An error code of zero indicates
successful completion of the asynchronous operation. On successful completion,
the buffer supplied to the original function call contains a hostent structure.
To access the elements of this structure, the original buffer address should be
cast to a hostent structure pointer and accessed as appropriate.
Note that if the error code is
WSAENOBUFS,
it indicates that the size of the
buffer specified by buflen in the original call was too small to contain
all the resultant information. In this case, the low 16 bits of lParam
contain the size of buffer required to supply ALL the requisite information.
If the application decides that the partial data is inadequate, it may reissue
the WSAAsyncGetHostByAddr() function call with a buffer large enough to
receive all the desired information (i.e. no smaller than the low 16 bits of
lParam).
The error code and buffer length should be extracted from the lParam
using the macros WSAGETASYNCERROR and WSAGETASYNCBUFLEN, defined in
winsock.h as:
#define WSAGETASYNCERROR(lParam) HIWORD(lParam)
#define WSAGETASYNCBUFLEN(lParam) LOWORD(lParam)
The use of these macros will maximize the portability of the source code for
the application.
Return Value
The return value specifies whether or not the asynchronous
operation was successfully initiated. Note that it does not imply
success or failure of the operation itself.
If the operation was successfully initiated, WSAAsyncGetHostByAddr()
returns a nonzero value of type HANDLE which is the asynchronous task handle
for the request. This value can be used in two ways. It can be used to cancel
the operation using
WSACancelAsyncRequest().
It can also be used to match up asynchronous operations and completion
messages, by examining the wParam message argument.
If the asynchronous operation could not be initiated,
WSAAsyncGetHostByAddr() returns a zero value, and a specific error
number may be retrieved by calling
WSAGetLastError().
Comments
The buffer supplied to this function is used by the Windows
Sockets implementation to construct a hostent structure together with the
contents of data areas referenced by members of the same hostent structure. To
avoid the WSAENOBUFS
error noted above, the application should provide a buffer
of at least MAXGETHOSTSTRUCT bytes (as defined in winsock.h).
Notes For Windows Sockets Suppliers
It is the responsibility of the Windows Sockets implementation
to ensure that messages are successfully posted to the application. If a
PostMessage() operation fails, the Windows Sockets implementation
must re-post that message as long as the window exists.
Windows Sockets suppliers should use the WSAMAKEASYNCREPLY macro when
constructing the lParam in the message.
Error Codes
The following error codes may be set when an application
window receives a message. As described above, they may be extracted from the
lParam in the reply message using the WSAGETASYNCERROR macro.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAENOBUFS
- No/insufficient buffer space is available
- WSAHOST_NOT_FOUND
- Authoritative Answer Host not found.
- WSATRY_AGAIN
- Non-Authoritative Host not found, or SERVERFAIL.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
The following errors may occur at the time of the function call, and
indicate that the asynchronous operation could not be initiated.
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEWOULDBLOCK
- The asynchronous operation cannot be scheduled at this time due to resource
or other constraints within the Windows Sockets implementation.
See Also
gethostbyaddr(),
WSACancelAsyncRequest()
Description
Get host information corresponding to a hostname -
asynchronous version.
#include <winsock.h>
HANDLE PASCAL FAR WSAAsyncGetHostByName ( HWND hWnd, unsigned
int wMsg, const char FAR * name, char FAR *
buf, int buflen);
- hWnd
- The handle of the window which should receive a message when the
asynchronous request completes.
- wMsg
- The message to be received when the asynchronous request completes.
- name
- Apointer to the name of the host.
- buf
- A pointer to the data area to receive the hostent data. Note that this
must be larger than the size of a hostent structure. This is because the data
area supplied is used by the Windows Sockets implementation to contain not only
a hostent structure but any and all of the data which is referenced by members
of the hostent structure. It is recommended that you supply a buffer of
MAXGETHOSTSTRUCT bytes.
- buflen
- The size of data area buf above.
Remarks
This function is an asynchronous version of
gethostbyname(), and is used to retrieve host name and address
information corresponding to a hostname. The Windows Sockets implementation
initiates the operation and returns to the caller immediately, passing back an
asynchronous task handle which the application may use to identify the
operation. When the operation is completed, the results (if any) are copied
into the buffer provided by the caller and a message is sent to the
application's window.
When the asynchronous operation is complete the application's window
hWnd receives message wMsg. The wParam argument contains
the asynchronous task handle as returned by the original function call. The
high 16 bits of lParam contain any error code. The error code may be
any error as defined in winsock.h. An error code of zero indicates
successful completion of the asynchronous operation. On successful completion,
the buffer supplied to the original function call contains a hostent structure.
To access the elements of this structure, the original buffer address should be
cast to a hostent structure pointer and accessed as appropriate.
Note that if the error code is
WSAENOBUFS,
it indicates that the size of the
buffer specified by buflen in the original call was too small to contain
all the resultant information. In this case, the low 16 bits of lParam
contain the size of buffer required to supply ALL the requisite information.
If the application decides that the partial data is inadequate, it may reissue
the WSAAsyncGetHostByName() function call with a buffer large enough to
receive all the desired information (i.e. no smaller than the low 16 bits of
lParam).
The error code and buffer length should be extracted from the lParam
using the macros WSAGETASYNCERROR and WSAGETASYNCBUFLEN, defined in
winsock.h as:
#define WSAGETASYNCERROR(lParam) HIWORD(lParam)
#define WSAGETASYNCBUFLEN(lParam) LOWORD(lParam)
The use of these macros will maximize the portability of the source code for
the application.
Return Value
The return value specifies whether or not the asynchronous
operation was successfully initiated. Note that it does not imply
success or failure of the operation itself.
If the operation was successfully initiated, WSAAsyncGetHostByName()
returns a nonzero value of type HANDLE which is the asynchronous task handle
for the request. This value can be used in two ways. It can be used to cancel
the operation using
WSACancelAsyncRequest().
It can also be used to match up asynchronous operations and completion
messages, by examining the wParam message argument.
If the asynchronous operation could not be initiated,
WSAAsyncGetHostByName() returns a zero value, and a specific error
number may be retrieved by calling
WSAGetLastError().
Comments
The buffer supplied to this function is used by the Windows
Sockets implementation to construct a hostent structure together with the
contents of data areas referenced by members of the same hostent structure. To
avoid the WSAENOBUFS
error noted above, the application should provide a buffer
of at least MAXGETHOSTSTRUCT bytes (as defined in winsock.h).
Notes For Windows Sockets Suppliers
It is the responsibility of the Windows Sockets implementation
to ensure that messages are successfully posted to the application. If a
PostMessage() operation fails, the Windows Sockets implementation
must re-post that message as long as the window exists.
Windows Sockets suppliers should use the WSAMAKEASYNCREPLY macro when
constructing the lParam in the message.
Error Codes
The following error codes may be set when an application
window receives a message. As described above, they may be extracted from the
lParam in the reply message using the WSAGETASYNCERROR macro.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAENOBUFS
- No/insufficient buffer space is available
- WSAHOST_NOT_FOUND
- Authoritative Answer Host not found.
- WSATRY_AGAIN
- Non-Authoritative Host not found, or SERVERFAIL.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
The following errors may occur at the time of the function call, and
indicate that the asynchronous operation could not be initiated.
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEWOULDBLOCK
- The asynchronous operation cannot be scheduled at this time due to resource
or other constraints within the Windows Sockets implementation.
See Also
gethostbyname(),
WSACancelAsyncRequest()
Description
Get protocol information corresponding to a protocol name -
asynchronous version.
#include <winsock.h>
HANDLE PASCAL FAR WSAAsyncGetProtoByName ( HWND hWnd,
unsigned int wMsg, const char FAR * name, char FAR
* buf, int buflen);
- hWnd
- The handle of the window which should receive a message when the
asynchronous request completes.
- wMsg
- The message to be received when the asynchronous request completes.
- name
- Apointer to the protocol name to be resolved.
- buf
- A pointer to the data area to receive the protoent data. Note that this
must be larger than the size of a protoent structure. This is because the data
area supplied is used by the Windows Sockets implementation to contain not only
a protoent structure but any and all of the data which is referenced by members
of the protoent structure. It is recommended that you supply a buffer of
MAXGETHOSTSTRUCT bytes.
- buflen
- The size of data area buf above.
Remarks
This function is an asynchronous version of
getprotobyname(),
and is used to retrieve the protocol name and number corresponding to a
protocol name. The Windows Sockets implementation initiates the operation and
returns to the caller immediately, passing back an asynchronous task
handle which the application may use to identify the operation. When the
operation is completed, the results (if any) are copied into the buffer
provided by the caller and a message is sent to the application's window.
When the asynchronous operation is complete the application's window
hWnd receives message wMsg. The wParam argument contains
the asynchronous task handle as returned by the original function call. The
high 16 bits of lParam contain any error code. The error code may be
any error as defined in winsock.h. An error code of zero indicates
successful completion of the asynchronous operation. On successful completion,
the buffer supplied to the original function call contains a protoent
structure. To access the elements of this structure, the original buffer
address should be cast to a protoent structure pointer and accessed as
appropriate.
Note that if the error code is
WSAENOBUFS,
it indicates that the size of the
buffer specified by buflen in the original call was too small to contain
all the resultant information. In this case, the low 16 bits of lParam
contain the size of buffer required to supply ALL the requisite information.
If the application decides that the partial data is inadequate, it may reissue
the WSAAsyncGetProtoByName() function call with a buffer large enough to
receive all the desired information (i.e. no smaller than the low 16 bits of
lParam).
The error code and buffer length should be extracted from the lParam
using the macros WSAGETASYNCERROR and WSAGETASYNCBUFLEN, defined in
winsock.h as:
#define WSAGETASYNCERROR(lParam) HIWORD(lParam)
#define WSAGETASYNCBUFLEN(lParam) LOWORD(lParam)
The use of these macros will maximize the portability of the source code for
the application.
Return Value
The return value specifies whether or not the asynchronous
operation was successfully initiated. Note that it does not imply
success or failure of the operation itself.
If the operation was successfully initiated, WSAAsyncGetProtoByName()
returns a nonzero value of type HANDLE which is the asynchronous task handle
for the request. This value can be used in two ways. It can be used to cancel
the operation using
WSACancelAsyncRequest().
It can also be used to match up asynchronous operations and completion
messages, by examining the wParam message argument.
If the asynchronous operation could not be initiated,
WSAAsyncGetProtoByName() returns a zero value, and a specific error
number may be retrieved by calling
WSAGetLastError().
Comments
The buffer supplied to this function is used by the Windows
Sockets implementation to construct a protoent structure together with the
contents of data areas referenced by members of the same protoent structure.
To avoid the WSAENOBUFS
error noted above, the application should provide a
buffer of at least MAXGETHOSTSTRUCT bytes (as defined in winsock.h).
Notes For Windows Sockets Suppliers
It is the responsibility of the Windows Sockets implementation
to ensure that messages are successfully posted to the application. If a
PostMessage() operation fails, the Windows Sockets implementation
must re-post that message as long as the window exists.
Windows Sockets suppliers should use the WSAMAKEASYNCREPLY macro when
constructing the lParam in the message.
Error Codes
The following error codes may be set when an application
window receives a message. As described above, they may be extracted from the
lParam in the reply message using the WSAGETASYNCERROR macro.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAENOBUFS
- No/insufficient buffer space is available
- WSAHOST_NOT_FOUND
- Authoritative Answer Host not found.
- WSATRY_AGAIN
- Non-Authoritative Host not found, or SERVERFAIL.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
The following errors may occur at the time of the function call, and
indicate that the asynchronous operation could not be initiated.
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEWOULDBLOCK
- The asynchronous operation cannot be scheduled at this time due to resource
or other constraints within the Windows Sockets implementation.
See Also
getprotobyname(),
WSACancelAsyncRequest()
Description
Get protocol information corresponding to a protocol number
- asynchronous version.
#include <winsock.h>
HANDLE PASCAL FAR WSAAsyncGetProtoByNumber ( HWND hWnd,
unsigned int wMsg, int number, char FAR *
buf, int buflen);
- hWnd
- The handle of the window which should receive a message when the
asynchronous request completes.
- wMsg
- The message to be received when the asynchronous request completes.
- number
- The protocol number to be resolved, in host byte order.
- buf
- A pointer to the data area to receive the protoent data. Note that this
must be larger than the size of a protoent structure. This is because the data
area supplied is used by the Windows Sockets implementation to contain not only
a protoent structure but any and all of the data which is referenced by members
of the protoent structure. It is recommended that you supply a buffer of
MAXGETHOSTSTRUCT bytes.
- buflen
- The size of data area buf above.
Remarks
This function is an asynchronous version of
getprotobynumber(),
and is used to retrieve the protocol name and number corresponding to a
protocol number. The Windows Sockets implementation initiates the operation
and returns to the caller immediately, passing back an asynchronous task
handle which the application may use to identify the operation. When the
operation is completed, the results (if any) are copied into the buffer
provided by the caller and a message is sent to the application's window.
When the asynchronous operation is complete the application's window
hWnd receives message wMsg. The wParam argument contains
the asynchronous task handle as returned by the original function call. The
high 16 bits of lParam contain any error code. The error code may be
any error as defined in winsock.h. An error code of zero indicates
successful completion of the asynchronous operation. On successful completion,
the buffer supplied to the original function call contains a protoent
structure. To access the elements of this structure, the original buffer
address should be cast to a protoent structure pointer and accessed as
appropriate.
Note that if the error code is
WSAENOBUFS,
it indicates that the size of the
buffer specified by buflen in the original call was too small to contain
all the resultant information. In this case, the low 16 bits of lParam
contain the size of buffer required to supply ALL the requisite information.
If the application decides that the partial data is inadequate, it may reissue
the WSAAsyncGetProtoByNumber() function call with a buffer large enough
to receive all the desired information (i.e. no smaller than the low 16 bits
of lParam).
The error code and buffer length should be extracted from the lParam
using the macros WSAGETASYNCERROR and WSAGETASYNCBUFLEN, defined in
winsock.h as:
#define WSAGETASYNCERROR(lParam) HIWORD(lParam)
#define WSAGETASYNCBUFLEN(lParam) LOWORD(lParam)
The use of these macros will maximize the portability of the source code for
the application.
Return Value
The return value specifies whether or not the asynchronous
operation was successfully initiated. Note that it does not imply
success or failure of the operation itself.
If the operation was successfully initiated, WSAAsyncGetProtoByNumber()
returns a nonzero value of type HANDLE which is the asynchronous task handle
for the request. This value can be used in two ways. It can be used to cancel
the operation using
WSACancelAsyncRequest().
It can also be used to match up asynchronous operations and completion
messages, by examining the wParam message argument.
If the asynchronous operation could not be initiated,
WSAAsyncGetProtoByNumber() returns a zero value, and a specific error
number may be retrieved by calling
WSAGetLastError().
Comments
The buffer supplied to this function is used by the Windows
Sockets implementation to construct a protoent structure together with the
contents of data areas referenced by members of the same protoent structure.
To avoid the WSAENOBUFS
error noted above, the application should provide a
buffer of at least MAXGETHOSTSTRUCT bytes (as defined in winsock.h).
Notes For Windows Sockets Suppliers
It is the responsibility of the Windows Sockets implementation
to ensure that messages are successfully posted to the application. If a
PostMessage() operation fails, the Windows Sockets implementation
must re-post that message as long as the window exists.
Windows Sockets suppliers should use the WSAMAKEASYNCREPLY macro when
constructing the lParam in the message.
Error Codes
The following error codes may be set when an application
window receives a message. As described above, they may be extracted from the
lParam in the reply message using the WSAGETASYNCERROR macro.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAENOBUFS
- No/insufficient buffer space is available
- WSAHOST_NOT_FOUND
- Authoritative Answer Host not found.
- WSATRY_AGAIN
- Non-Authoritative Host not found, or SERVERFAIL.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
The following errors may occur at the time of the function call, and
indicate that the asynchronous operation could not be initiated.
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEWOULDBLOCK
- The asynchronous operation cannot be scheduled at this time due to resource
or other constraints within the Windows Sockets implementation.
See Also
getprotobynumber(),
WSACancelAsyncRequest()
Description
Get service information corresponding to a service name and
port -- asynchronous version.
#include <winsock.h>
HANDLE PASCAL FAR WSAAsyncGetServByName ( HWND hWnd, unsigned
int wMsg, const char FAR * name, const char FAR *
proto, char FAR * buf, int buflen
);
- hWnd
- The handle of the window which should receive a message when the
asynchronous request completes.
- wMsg
- The message to be received when the asynchronous request completes.
- name
- A pointer to a service name.
- proto
- A pointer to a protocol name. This may be NULL, in which case
WSAAsyncGetServByName() will search for the first service entry for
which s_name or one of the s_aliases matches the given
name. Otherwise WSAAsyncGetServByName() matches both name
and proto.
- buf
- A pointer to the data area to receive the servent data. Note that this
must be larger than the size of a servent structure. This is because the data
area supplied is used by the Windows Sockets implementation to contain not only
a servent structure but any and all of the data which is referenced by members
of the servent structure. It is recommended that you supply a buffer of
MAXGETHOSTSTRUCT bytes.
- buflen
- The size of data area buf above.
Remarks
This function is an asynchronous version of
getservbyname(),
and is used to retrieve service information corresponding to a service name.
The Windows Sockets implementation initiates the operation and returns to the
caller immediately, passing back an asynchronous task handle which the
application may use to identify the operation. When the operation is
completed, the results (if any) are copied into the buffer provided by the
caller and a message is sent to the application's window.
When the asynchronous operation is complete the application's window
hWnd receives message wMsg. The wParam argument contains
the asynchronous task handle as returned by the original function call. The
high 16 bits of lParam contain any error code. The error code may be
any error as defined in winsock.h. An error code of zero indicates
successful completion of the asynchronous operation. On successful completion,
the buffer supplied to the original function call contains a hostent structure.
To access the elements of this structure, the original buffer address should be
cast to a hostent structure pointer and accessed as appropriate.
Note that if the error code is
WSAENOBUFS, it indicates that the size of the
buffer specified by buflen in the original call was too small to contain
all the resultant information. In this case, the low 16 bits of lParam
contain the size of buffer required to supply ALL the requisite information.
If the application decides that the partial data is inadequate, it may reissue
the WSAAsyncGetServByName() function call with a buffer large enough to
receive all the desired information (i.e. no smaller than the low 16 bits of
lParam).
The error code and buffer length should be extracted from the lParam
using the macros WSAGETASYNCERROR and WSAGETASYNCBUFLEN, defined in
winsock.h as:
#define WSAGETASYNCERROR(lParam) HIWORD(lParam)
#define WSAGETASYNCBUFLEN(lParam) LOWORD(lParam)
The use of these macros will maximize the portability of the source code for
the application.
Return Value
The return value specifies whether or not the asynchronous
operation was successfully initiated. Note that it does not imply
success or failure of the operation itself.
If the operation was successfully initiated, WSAAsyncGetServByName()
returns a nonzero value of type HANDLE which is the asynchronous task handle
for the request. This value can be used in two ways. It can be used to cancel
the operation using
WSACancelAsyncRequest().
It can also be used to match up asynchronous operations and completion
messages, by examining the wParam message argument.
If the asynchronous operation could not be initiated,
WSAAsyncGetHostByAddr() returns a zero value, and a specific error
number may be retrieved by calling
WSAGetLastError().
Comments
The buffer supplied to this function is used by the Windows
Sockets implementation to construct a hostent structure together with the
contents of data areas referenced by members of the same hostent structure. To
avoid the WSAENOBUFS
error noted above, the application should provide a buffer
of at least MAXGETHOSTSTRUCT bytes (as defined in winsock.h).
Notes For Windows Sockets Suppliers
It is the responsibility of the Windows Sockets implementation
to ensure that messages are successfully posted to the application. If a
PostMessage() operation fails, the Windows Sockets implementation
must re-post that message as long as the window exists.
Windows Sockets suppliers should use the WSAMAKEASYNCREPLY macro when
constructing the lParam in the message.
Error Codes
The following error codes may be set when an application
window receives a message. As described above, they may be extracted from the
lParam in the reply message using the WSAGETASYNCERROR macro.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAENOBUFS
- No/insufficient buffer space is available
- WSAHOST_NOT_FOUND
- Authoritative Answer Host not found.
- WSATRY_AGAIN
- Non-Authoritative Host not found, or SERVERFAIL.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
The following errors may occur at the time of the function call, and
indicate that the asynchronous operation could not be initiated.
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEWOULDBLOCK
- The asynchronous operation cannot be scheduled at this time due to resource
or other constraints within the Windows Sockets implementation.
See Also
getservbyname(),
WSACancelAsyncRequest()
Description
Get service information corresponding to a port and protocol
- asynchronous version.
#include <winsock.h>
HANDLE PASCAL FAR WSAAsyncGetServByPort ( HWND hWnd, unsigned
int wMsg, int port, const char FAR *
proto, char FAR * buf, int buflen
);
- hWnd
- The handle of the window which should receive a message when the
asynchronous request completes.
- wMsg
- The message to be received when the asynchronous request completes.
- port
- The port for the service, in network byte order.
- proto
- A pointer to a protocol name. This may be NULL, in which case
WSAAsyncGetServByPort() will search for the first service entry for
which s_port match the given port. Otherwise
WSAAsyncGetServByPort() matches both port and proto.
- buf
- A pointer to the data area to receive the servent data. Note that this
must be larger than the size of a servent structure. This is because the data
area supplied is used by the Windows Sockets implementation to contain not only
a servent structure but any and all of the data which is referenced by members
of the servent structure. It is recommended that you supply a buffer of
MAXGETHOSTSTRUCT bytes.
- buflen
- The size of data area buf above.
Remarks
This function is an asynchronous version of
getservbyport(),
and is used to retrieve service information corresponding to a port number.
The Windows Sockets implementation initiates the operation and returns to the
caller immediately, passing back an asynchronous task handle which the
application may use to identify the operation. When the operation is
completed, the results (if any) are copied into the buffer provided by the
caller and a message is sent to the application's window.
When the asynchronous operation is complete the application's window
hWnd receives message wMsg. The wParam argument contains
the asynchronous task handle as returned by the original function call. The
high 16 bits of lParam contain any error code. The error code may be
any error as defined in winsock.h. An error code of zero indicates
successful completion of the asynchronous operation. On successful completion,
the buffer supplied to the original function call contains a servent structure.
To access the elements of this structure, the original buffer address should be
cast to a servent structure pointer and accessed as appropriate.
Note that if the error code is
WSAENOBUFS, it indicates that the size of the
buffer specified by buflen in the original call was too small to contain
all the resultant information. In this case, the low 16 bits of lParam
contain the size of buffer required to supply ALL the requisite information.
If the application decides that the partial data is inadequate, it may reissue
the WSAAsyncGetServByPort() function call with a buffer large enough to
receive all the desired information (i.e. no smaller than the low 16 bits of
lParam).
The error code and buffer length should be extracted from the lParam
using the macros WSAGETASYNCERROR and WSAGETASYNCBUFLEN, defined in
winsock.h as:
#define WSAGETASYNCERROR(lParam) HIWORD(lParam)
#define WSAGETASYNCBUFLEN(lParam) LOWORD(lParam)
The use of these macros will maximize the portability of the source code for
the application.
Return Value
The return value specifies whether or not the asynchronous
operation was successfully initiated. Note that it does not imply
success or failure of the operation itself.
If the operation was successfully initiated, WSAAsyncGetServByPort()
returns a nonzero value of type HANDLE which is the asynchronous task handle
for the request. This value can be used in two ways. It can be used to cancel
the operation using
WSACancelAsyncRequest().
It can also be used to match up asynchronous operations and completion
messages, by examining the wParam message argument.
If the asynchronous operation could not be initiated,
WSAAsyncGetServByPort() returns a zero value, and a specific error
number may be retrieved by calling
WSAGetLastError().
Comments
The buffer supplied to this function is used by the Windows
Sockets implementation to construct a servent structure together with the
contents of data areas referenced by members of the same servent structure. To
avoid the WSAENOBUFS
error noted above, the application should provide a buffer
of at least MAXGETHOSTSTRUCT bytes (as defined in winsock.h).
Notes For Windows Sockets Suppliers
It is the responsibility of the Windows Sockets implementation
to ensure that messages are successfully posted to the application. If a
PostMessage() operation fails, the Windows Sockets implementation
must re-post that message as long as the window exists.
Windows Sockets suppliers should use the WSAMAKEASYNCREPLY macro when
constructing the lParam in the message.
Error Codes
The following error codes may be set when an application
window receives a message. As described above, they may be extracted from the
lParam in the reply message using the WSAGETASYNCERROR macro.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAENOBUFS
- No/insufficient buffer space is available
- WSAHOST_NOT_FOUND
- Authoritative Answer Host not found.
- WSATRY_AGAIN
- Non-Authoritative Host not found, or SERVERFAIL.
- WSANO_RECOVERY
- Non recoverable errors, FORMERR, REFUSED, NOTIMP.
- WSANO_DATA
- Valid name, no data record of requested type.
The following errors may occur at the time of the function call, and
indicate that the asynchronous operation could not be initiated.
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEWOULDBLOCK
- The asynchronous operation cannot be scheduled at this time due to resource
or other constraints within the Windows Sockets implementation.
See Also
getservbyport(),
WSACancelAsyncRequest()
Description
Request event notification for a socket.
#include <winsock.h>
int PASCAL FAR WSAAsyncSelect ( SOCKET s, HWND
hWnd, unsigned int wMsg, long lEvent
);
- s
- A descriptor identifying the socket for which event notification is
required.
- hWnd
- A handle identifying the window which should receive a message when a
network event occurs.
- wMsg
- The message to be received when a network event occurs.
- lEvent
- A bitmask which specifies a combination of network events in which the
application is interested.
Remarks
This function is used to request that the Windows Sockets DLL
should send a message to the window hWnd whenever it detects any of the
network events specified by the lEvent parameter. The message which
should be sent is specified by the wMsg parameter. The socket for which
notification is required is identified by s.
The lEvent parameter is constructed by or'ing any of the values
specified in the following list.
- FD_READ
- Want to receive notification of readiness for reading
- FD_WRITE
- Want to receive notification of readiness for writing
- FD_OOB
- Want to receive notification of the arrival of out-of-band data
- FD_ACCEPT
- Want to receive notification of incoming connections
- FD_CONNECT
- Want to receive notification of completed connection
- FD_CLOSE
- Want to receive notification of socket closure
Issuing a WSAAsyncSelect() for a socket cancels any previous
WSAAsyncSelect() for the same socket. For example, to receive
notification for both reading and writing, the application must call
WSAAsyncSelect() with both FD_READ and FD_WRITE, as follows:
rc = WSAAsyncSelect(s, hWnd, wMsg, FD_READ|FD_WRITE);
It is not possible to specify different messages for different events. The
following code will not work; the second call will cancel the effects of
the first, and only FD_WRITE events will be reported with message wMsg2:
rc = WSAAsyncSelect(s, hWnd, wMsg1, FD_READ);
rc = WSAAsyncSelect(s, hWnd, wMsg2, FD_WRITE);
To cancel all notification -- i.e., to indicate that the Windows Sockets
implementation should send no further messages related to network events on the
socket -- lEvent should be set to zero.
rc = WSAAsyncSelect(s, hWnd, 0, 0);
Although in this instance WSAAsyncSelect() immediately disables event
message posting for the socket, it is possible that messages may be waiting in
the application's message queue. The application must therefore be prepared to
receive network event messages even after cancellation. Closing a socket with
closesocket()
also cancels WSAAsyncSelect() message sending, but the same caveat
about messages in the queue prior to the
closesocket()
still applies.
Since an
accept()'ed
socket has the same properties as the listening socket used to accept it, any
WSAAsyncSelect() events set for the listening socket apply to the
accepted socket. For example, if a listening socket has WSAAsyncSelect()
events FD_ACCEPT, FD_READ, and FD_WRITE, then any socket accepted on that
listening socket will also have FD_ACCEPT, FD_READ, and FD_WRITE events with
the same wMsg value used for messages. If a different wMsg or
events are desired, the application should call WSAAsyncSelect(),
passing the accepted socket and the desired new information.
[Note: There is a timing window between the
accept()
call and the call to WSAAsyncSelect() to change the events or
wMsg. An application which desires a different wMsg for the
listening and
accept()'ed
sockets should ask for only FD_ACCEPT events on the listening socket, then set
appropriate events after the
accept().
Since FD_ACCEPT is never sent for a connected socket and FD_READ, FD_WRITE,
FD_OOB, and FD_CLOSE are never sent for listening sockets, this will not impose
difficulties.]
When one of the nominated network events occurs on the specified socket
s, the application's window hWnd receives message wMsg.
The wParam argument identifies the socket on which a network event has
occurred. The low word of lParam specifies the network event that has
occurred. The high word of lParam contains any error code. The error
code be any error as defined in winsock.h.
The error and event codes may be extracted from the lParam using the
macros WSAGETSELECTERROR and WSAGETSELECTEVENT, defined in winsock.h
as:
#define WSAGETSELECTERROR(lParam) HIWORD(lParam)
#define WSAGETSELECTEVENT(lParam) LOWORD(lParam)
The use of these macros will maximize the portability of the source code for
the application.
The possible network event codes which may be returned are as follows:
- FD_READ
- Socket s ready for reading
- FD_WRITE
- Socket s ready for writing
- FD_OOB
- Out-of-band data ready for reading on socket s.
- FD_ACCEPT
- Socket s ready for accepting a new incoming connection
- FD_CONNECT
- Connection on socket s completed
- FD_CLOSE
- Connection identified by socket s has been closed
Return Value
The return value is 0 if the application's declaration of
interest in the network event set was successful. Otherwise the value
SOCKET_ERROR is returned, and a specific error number may be retrieved by
calling WSAGetLastError().
Comments
Although WSAAsyncSelect() can be called with interest in
multiple events, the application window will receive a single message for each
network event.
As in the case of the select() function, WSAAsyncSelect() will
frequently be used to determine when a data transfer operation (send()
or recv()) can be issued with the expectation of immediate success.
Nevertheless, a robust application must be prepared for the possibility that it
may receive a message and issue a Windows Sockets API call which returns
WSAEWOULDBLOCK
immediately. For example, the following sequence of events is
possible:
-
data arrives on socket s; Windows Sockets posts
WSAAsyncSelect message
-
application processes some other message
-
while processing, application issues an
ioctlsocket(s, FIONREAD...) and notices that
there is data ready to be read
-
application issues a recv(s,...) to read the
data
-
application loops to process next message, eventually reaching the
WSAAsyncSelect message indicating that data is ready to read
-
application issues recv(s,...), which fails
with the error WSAEWOULDBLOCK.
Other sequences are possible.
The Windows Sockets DLL will not continually flood an application with messages
for a particular network event. Having successfully posted notification of a
particular event to an application window, no further message(s) for that
network event will be posted to the application window until the application
makes the function call which implicitly re-enables notification of that
network event.
- FD_READ
- recv() or recvfrom()
- FD_WRITE
- send() or sendto()
- FD_OOB
- recv()
- FD_ACCEPT
- accept()
- FD_CONNECT
- NONE
- FD_CLOSE
- NONE
Any call to the reenabling routine, even one which fails, results in reenabling
of message posting for the relevent event.
For FD_READ, FD_OOB, and FD_ACCEPT events, message posting is
"level-triggerred." This means that if the reenabling routine is called and
the relevent event is still valid after the call, a WSAAsyncSelect()
message is posted to the application. This allows an application to be
event-driven and not concern itself with the amount of data that arrives at any
one time. Consider the following sequence:
-
Windows Sockets DLL receives 100 bytes of data on socket s and posts
an FD_READ message.
- The application issues recv( s, buffptr, 50, 0) to read 50 bytes.
-
The Windows Sockets DLL posts another FD_READ message since there is still
data to be read.
With these semantics, an application need not read all available data
in response to an FD_READ message--a single
recv()
in response to each FD_READ message is appropriate. If an application
issues multiple
recv()
calls in response to a single FD_READ, it may receive multiple FD_READ
messages. Such an application may wish to disable FD_READ messages before
starting the
recv()
calls by calling WSAAsyncSelect() with the FD_READ event not set.
If an event is true when the application initially calls
WSAAsyncSelect() or when the reenabling function is called, then a
message is posted as appropriate. For example, if an application calls
listen(),
a connect attempt is made, then the application calls WSAAsyncSelect()
specifying that it wants to receive FD_ACCEPT messages for the socket, the
Windows Sockets implementation posts an FD_ACCEPT message immediately.
The FD_WRITE event is handled slightly differently. An FD_WRITE message is
posted when a socket is first connected with
connect()
or accepted with
accept(),
and then after a
send()
or
sendto()
fails with WSAEWOULDBLOCK
and buffer space becomes available. Therefore,
an application can assume that sends are possible starting from the first
FD_WRITE message and lasting until a send returns
WSAEWOULDBLOCK. After such a
failure the application will be notified that sends are again possible with an
FD_WRITE message.
The FD_OOB event is used only when a socket is configured to receive
out-of-band data separately. If the socket is configured to receive
out-of-band data in-line, the out-of-band (expedited) data is treated as normal
data and the application should register an interest in, and will receive,
FD_READ events, not FD_OOB events. An application may set or inspect
the way in which out-of-band data is to be handled by using
setsockopt()
or
getsockopt
for the SO_OOBINLINE option.
The error code in an FD_CLOSE message indicates whether the socket close was
graceful or abortive. If the error code is 0, then the close was graceful; if
the error code is
WSAECONNRESET, then the socket's virtual socket was
abortively disconnected. This only applies to sockets of type SOCK_STREAM.
The FD_CLOSE message is posted when a close indication is received for the
virtual circuit corresponding to the socket. In TCP terms, this means that the
FD_CLOSE is posted when the connection goes into the FIN WAIT or CLOSE WAIT
states. This results from the remote end performing a
shutdown()
on the send side or a
closesocket().
Please note your application will receive ONLY an FD_CLOSE message to indicate
closure of a virtual circuit. It will NOT receive an FD_READ message to
indicate this condition.
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINVAL
- Indicates that one of the specified parameters was invalid
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- Additional error codes may be set when an application window receives a
message. This error code is extracted from the lParam in the reply
message using the WSAGETSELECTERROR macro. Possible error codes for each
network event are:
Event: FD_CONNECT
Error Codes
- WSAEADDRINUSE
- The specified address is already in use.
- WSAEADDRNOTAVAIL
- The specified address is not available from the local machine.
- WSAEAFNOSUPPORT
- Addresses in the specified family cannot be used with this socket.
- WSAECONNREFUSED
- The attempt to connect was forcefully rejected.
- WSAEDESTADDRREQ
- A destination address is required.
- WSAEFAULT
- The namelen argument is incorrect.
- WSAEINVAL
- The socket is already bound to an address.
- WSAEISCONN
- The socket is already connected.
- WSAEMFILE
- No more file descriptors are available.
- WSAENETUNREACH
- The network can't be reached from this host at this time.
- WSAENOBUFS
- No buffer space is available. The socket cannot be connected.
- WSAENOTCONN
- The socket is not connected.
- WSAENOTSOCK
- The descriptor is a file, not a socket.
- WSAETIMEDOUT
- Attempt to connect timed out without establishing a connection
Event: FD_CLOSE
Error Codes
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAECONNRESET
- The connection is reset by the remote side.
- WSAECONNABORTED
- The connection was aborted due to timeout or other failure.
Event: FD_READ
Event: FD_WRITE
Event: FD_OOB
Event: FD_ACCEPT
Error Code
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
Notes For Windows Sockets Suppliers
It is the responsibility of the Windows Sockets Supplier to
ensure that messages are successfully posted to the application. If a
PostMessage() operation fails, the Windows Sockets implementation
must re-post that message as long as the window exists.
Windows Sockets suppliers should use the WSAMAKESELECTREPLY macro when
constructing the lParam in the message.
When a socket is closed, the Windows Sockets Supplier should purge any messages
remaining for posting to the application window. However the application must
be prepared to receive, and discard, any messages which may have been posted
prior to the
closesocket().
See Also
select()
Description
Cancel an incomplete asynchronous operation.
#include <winsock.h>
int PASCAL FAR WSACancelAsyncRequest ( HANDLE hAsyncTaskHandle
);
- hAsyncTaskHandle
- Specifies the asynchronous operation to be canceled.
Remarks
The WSACancelAsyncRequest() function is used to cancel an
asynchronous operation which was initiated by one of the
WSAAsyncGetXByY() functions such as
WSAAsyncGetHostByName().
The operation to be canceled is identified by the hAsyncTaskHandle
parameter, which should be set to the asynchronous task handle as returned by
the initiating function.
Return Value The value returned by
WSACancelAsyncRequest() is 0 if the operation was successfully canceled.
Otherwise the value SOCKET_ERROR is returned, and a specific error number may
be retrieved by calling
WSAGetLastError().
Comments
An attempt to cancel an existing asynchronous
WSAAsyncGetXByY() operation can fail with an error code of
WSAEALREADY
for two reasons. Firstly, the original operation has already completed and the
application has dealt with the resultant message. Secondly, the original
operation has already completed but the resultant message is still waiting in
the application window queue.
Notes For Windows Sockets Suppliers
It is unclear whether the application can usefully distinguish
between WSAEINVAL and
WSAEALREADY,
since in both cases the error indicates that
there is no asynchronous operation in progress with the indicated handle.
[Trivial exception: 0 is always an invalid asynchronous task handle.] The
Windows Sockets specification does not prescribe how a conformant Windows
Sockets implementation should distinguish between the two cases. For maximum
portability, a Windows Sockets application should treat the two errors as
equivalent.
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINVAL
- Indicates that the specified asynchronous task handle was invalid
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
- WSAEALREADY
- The asynchronous routine being canceled has already completed.
See Also
WSAAsyncGetHostByAddr(),
WSAAsyncGetHostByName(),
WSAAsyncGetProtoByNumber(),
WSAAsyncGetProtoByName(),
WSAAsyncGetHostByName(),
WSAAsyncGetServByPort(),
WSAAsyncGetServByName().
Description
Cancel a blocking call which is currently in progress.
#include <winsock.h>
int PASCAL FAR WSACancelBlockingCall ( void );
Remarks
This function cancels any outstanding blocking operation for
this task. It is normally used in two situations:
-
An application is processing a message which has been received while a
blocking call is in progress. In this case,
WSAIsBlocking() will be true.
-
A blocking call is in progress, and Windows Sockets has called back to the
application's "blocking hook" function (as established by
WSASetBlockingHook()).
In each case, the original blocking call will terminate as soon as possible
with the error WSAEINTR.
(In (1), the termination will not take place until
Windows message scheduling has caused control to revert to the blocking routine
in Windows Sockets. In (2), the blocking call will be terminated as soon as
the blocking hook function completes.)
In the case of a blocking
connect()
operation, the Windows Sockets implementation will terminate the blocking call
as soon as possible, but it may not be possible for the socket resources to be
released until the connection has completed (and then been reset) or timed out.
This is likely to be noticeable only if the application immediately tries to
open a new socket (if no sockets are available), or to
connect()
to the same peer.
Cancelling an
accept()
or a
select()
call does not adversely impact the sockets passed to these calls. Only the
particular call fails; any operation that was legal before the cancel is legal
after the cancel, and the state of the socket is not affected in any way.
Cancelling any operation other than
accept()
and
select()
can leave the socket in an indeterminate state. If an application cancels
a blocking operation on a socket, the only operation that the application can
depend on being able to perform on the socket is a call to
closesocket(),
although other operations may work on some Windows Sockets implementations. If
an application desires maximum portability, it must be careful not to depend on
performing operations after a cancel. An application may reset the connection
by setting the timeout on SO_LINGER to 0.
If a cancel operation comprimised the integrity of a SOCK_STREAM's data stream
in any way, the Windows Sockets implementation must reset the connection and
fail all future operations other than
closesocket()
with WSAECONNABORTED.
Return Value
The value returned by WSACancelBlockingCall() is 0
if the operation was successfully canceled. Otherwise the value SOCKET_ERROR
is returned, and a specific error number may be retrieved by calling
WSAGetLastError().
Comments Note that it is possible that the network operation completes
before the WSACancelBlockingCall() is processed, for example if data is
received into the user buffer at interrupt time while the application is in a
blocking hook. In this case, the blocking operation will return successfully
as if WSACancelBlockingCall() had never been called. Note that the
WSACancelBlockingCall() still succeeds in this case; the only way to
know with certainty that an operation was actually cancelled is to check for a
return code of WSAEINTR
from the blocking call.
Error Codes
-
WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINVAL
- Indicates that there is no outstanding blocking call.
Description
Terminate use of the Windows Sockets DLL.
#include <winsock.h>
int PASCAL FAR WSACleanup ( void );
Remarks
An application is required to perform a (successful)
WSAStartup()
call before it can use Windows Sockets services. When it has completed the use
of Windows Sockets, the application must call WSACleanup() to deregister
itself from a Windows Sockets implementation and allow the implementation to
free any resources allocated on behalf of the application or DLL. Any open
SOCK_STREAM sockets that are connected when WSACleanup() is called are
reset; sockets which have been closed with
closesocket()
but which still have pending data to be sent are not affected--the pending
data is still sent.
There must be a call to WSACleanup() for every call to
WSAStartup()
made by a task. Only the final WSACleanup() does the actual
cleanup; the preceding calls simply decrement an internal reference count in
the Windows Sockets DLL. A naive application may ensure that WSACleanup()
was called enough times by calling WSACleanup() in a loop until it
returns
WSAENOTINITIALISED.
Return Value
The return value is 0 if the operation was successful.
Otherwise the value SOCKET_ERROR is returned, and a specific error number may
be retrieved by calling
WSAGetLastError().
Comments Attempting to call WSACleanup() from within a blocking
hook and then failing to check the return code is a common Windows Sockets
programming error. If an application needs to quit while a blocking call is
outstanding, the application must first cancel the blocking call with
WSACancelBlockingCall()
then issue the WSACleanup() call once control has been returned to the
application.
Notes For Windows Sockets Suppliers
Well-behaved Windows Sockets applications will make a
WSACleanup() call to indicate deregistration from a Windows Sockets
implementation. This function can thus, for example, be utilized to free up
resources allocated to the specific application.
A Windows Sockets implementation must be prepared to deal with an application
which terminates without invoking WSACleanup() -- for example, as a
result of an error.
In a multithreaded environment, WSACleanup() terminates Windows Sockets
operations for all threads.
A Windows Sockets implementation must ensure that WSACleanup() leaves
things in a state in which the application can invoke WSAStartup() to
re-establish Windows Sockets usage.
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
See Also
WSAStartup()
Description
Get the error status for the last operation which
failed.
#include <winsock.h>
int PASCAL FAR WSAGetLastError ( void );
Remarks
This function returns the last network error that occurred.
When a particular Windows Sockets API function indicates that an error has
occurred, this function should be called to retrieve the appropriate error code.
Return Value
The return value indicates the error code for the last
Windows Sockets API routine performed by this thread.
Notes For Windows Sockets Suppliers
The use of the WSAGetLastError() function to retrieve
the last error code, rather than relying on a global error variable (cf.
errno), is required in order to provide compatibility with future
multi-threaded environments.
Note that in a Win16 environment WSAGetLastError() is used to retrieve
only Windows Sockets API errors. In a Win32 environment,
WSAGetLastError() will invoke GetLastError(), which is used to
retrieve the error status for all Win32 API functions on a per-thread basis.
For portability, an application should use WSAGetLastError()
immediately after the Windows Sockets API function which failed.
See Also
WSASetLastError()
Description
Determine if a blocking call is in progress.
#include <winsock.h>
BOOL PASCAL FAR WSAIsBlocking ( void );
Remarks
This function allows a task to determine if it is executing
while waiting for a previous blocking call to complete.
Return Value
The return value is TRUE if there is an outstanding
blocking function awaiting completion. Otherwise, it is FALSE.
Comments
Although a call issued on a blocking socket appears to an
application program as though it "blocks", the Windows Sockets DLL has to
relinquish the processor to allow other applications to run. This means that
it is possible for the application which issued the blocking call to be
re-entered, depending on the message(s) it receives. In this instance, the
WSAIsBlocking() function can be used to ascertain whether the task has
been re-entered while waiting for an outstanding blocking call to complete.
Note that Windows Sockets prohibits more than one outstanding call per thread.
Notes For Windows Sockets Suppliers
A Windows Sockets implementation must prohibit more than one
outstanding blocking call per thread.
Description
Establish an application-specific blocking hook function.
#include <winsock.h>
FARPROC PASCAL FAR WSASetBlockingHook ( FARPROC lpBlockFunc
);
- lpBlockFunc
- A pointer to the procedure instance address of the blocking function to be
installed.
Remarks
This function installs a new function which a Windows Sockets
implementation should use to implement blocking socket function calls.
A Windows Sockets implementation includes a default mechanism by which blocking
socket functions are implemented. The function WSASetBlockingHook()
gives the application the ability to execute its own function at "blocking"
time in place of the default function.
When an application invokes a blocking Windows Sockets API operation, the
Windows Sockets implementation initiates the operation and then enters a loop
which is equivalent to the following pseudocode:
for(;;) {
/* flush messages for good user response */
while(BlockingHook())
;
/* check for WSACancelBlockingCall() */
if(operation_cancelled())
break;
/* check to see if operation completed */
if(operation_complete())
break; /* normal completion */
}
Note that Windows Sockets implementations may perform the above steps in a
different order; for example, the check for operation complete may occur before
calling the blocking hook. The default BlockingHook() function is
equivalent to:
BOOL DefaultBlockingHook(void) {
MSG msg;
BOOL ret;
/* get the next message if any */
ret = (BOOL)PeekMessage(&msg,NULL,0,0,PM_REMOVE);
/* if we got one, process it */
if (ret) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
/* TRUE if we got a message */
return ret;
}
The WSASetBlockingHook() function is provided to support those
applications which require more complex message processing -- for example, those
employing the MDI (multiple document interface) model. It is not
intended as a mechanism for performing general applications functions. In
particular, the only Windows Sockets API function which may be issued from a
custom blocking hook function is
WSACancelBlockingCall(),
which will cause the blocking loop to terminate.
This function must be implemented on a per-task basis for non-multithreaded
versions of Windows and on a per-thread basis for multithreaded versions of
Windows such as Windows NT. It thus provides for a particular task or thread
to replace the blocking mechanism without affecting other tasks or threads.
In multithreaded versions of Windows, there is no default blocking
hook--blocking calls block the thread that makes the call. However, an
application may install a specific blocking hook by calling
WSASetBlockingHook().
This allows easy portability of applications that depend on the blocking
hook behavior.
Return Value
The return value is a pointer to the procedure-instance of
the previously installed blocking function. The application or library that
calls the WSASetBlockingHook() function should save this return value so
that it can be restored if necessary. (If "nesting" is not important, the
application may simply discard the value returned by
WSASetBlockingHook() and eventually use
WSAUnhookBlockingHook()
to restore the default mechanism.) If the operation fails, a NULL pointer is
returned, and a specific error number may be retrieved by calling
WSAGetLastError().
Notes For Windows Sockets Suppliers
This function must be implemented on a per-thread basis. It
thus provides for a particular thread to replace the blocking mechanism without
affecting other threads.
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
- WSAENETDOWN
- The Windows Sockets implementation has detected that the network subsystem
has failed.
- WSAEINPROGRESS
- A blocking Windows Sockets operation is in progress.
See Also
WSAUnhookBlockingHook()
Description
Set the error code which can be retrieved by
WSAGetLastError().
#include <winsock.h>
void PASCAL FAR WSASetLastError ( int iError
);
Remarks
This function allows an application to set the error code to be
returned by a subsequent
WSAGetLastError()
call for the current thread. Note that any subsequent Windows Sockets routine
called by the application will override the error code as set by this
routine.
- iError
- Specifies the error code to be returned by a subsequent
WSAGetLastError()
call.
Notes For Windows Sockets Suppliers
In a Win32 environment, this function will invoke
SetLastError().
Return Value
None.
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup()
must occur before using this API.
See Also
WSAGetLastError()
Description
#include <winsock.h>
int PASCAL FAR WSAStartup ( WORD wVersionRequired, LPWSADATA
lpWSAData );
- wVersionRequired
- The highest version of Windows Sockets API support that the caller can use.
The high order byte specifies the minor version (revision) number; the
low-order byte specifies the major version number.
- lpWSAData
- A pointer to the WSADATA data structure that is to receive details
of the Windows Sockets implementation.
Remarks
This function must be the first Windows Sockets function
called by an application or DLL. It allows an application to specify the
version of Windows Sockets API required and to retrieve details of the specific
Windows Sockets implementation. The application may only issue further Windows
Sockets API functions after a successful WSAStartup() invocation.
In order to support future Windows Sockets implementations and applications
which may have functionality differences from Windows Sockets 1.1, a
negotiation takes place in WSAStartup(). The caller of
WSAStartup() and the Windows Sockets DLL indicate to each other the
highest version that they can support, and each confirms that the other's
highest version is acceptable. Upon entry to WSAStartup(), the Windows
Sockets DLL examines the version requested by the application. If this version
is higher than the lowest version supported by the DLL, the call succeeds and
the DLL returns in wHighVersion the highest version it supports and in
wVersion the minimum of its high version and wVersionRequested.
The Windows Sockets DLL then assumes that the application will use
wVersion. If the wVersion field of the WSADATA structure
is unacceptable to the caller, it should call
WSACleanup()
and either search for another Windows Sockets DLL or fail to initialize.
This negotiation allows both a Windows Sockets DLL and a Windows Sockets
application to support a range of Windows Sockets versions. An application can
successfully utilize a Windows Sockets DLL if there is any overlap in the
version ranges. The following chart gives examples of how WSAStartup()
works in conjunction with different application and Windows Sockets DLL
versions:
App versions DLL Versions wVersionRequested wVersion wHighVersion End Result
------------ ------------ ----------------- -------- ------------ ----------
1.1 1.1 1.1 1.1 1.1 use 1.1
1.0 1.1 1.0 1.1 1.0 1.0 use 1.0
1.0 1.0 1.1 1.0 1.0 1.1 use 1.0
1.1 1.0 1.1 1.1 1.1 1.1 use 1.1
1.1 1.0 1.1 1.0 1.0 App fails
1.0 1.1 1.0 --- --- NotSupp
1.0 1.1 1.0 1.1 1.1 1.1 1.1 use 1.1
1.1 2.0 1.1 2.0 1.1 1.1 use 1.1
2.0 1.1 2.0 1.1 1.1 App fails
The following code fragment demonstrates how an application which supports only
version 1.1 of Windows Sockets makes a WSAStartup() call:
WORD wVersionRequested;
WSADATA wsaData;
int err;
wVersionRequested = MAKEWORD( 1, 1 );
err = WSAStartup( wVersionRequested, &wsaData );
if ( err != 0 ) {
/* Tell the user that we couldn't find a useable */
/* winsock.dll. */
return;
}
/* Confirm that the Windows Sockets DLL supports 1.1.*/
/* Note that if the DLL supports versions greater */
/* than 1.1 in addition to 1.1, it will still return */
/* 1.1 in wVersion since that is the version we */
/* requested. */
if ( LOBYTE( wsaData.wVersion ) != 1 ||
HIBYTE( wsaData.wVersion ) != 1 ) {
/* Tell the user that we couldn't find a useable */
/* winsock.dll. */
WSACleanup( );
return;
}
/* The Windows Sockets DLL is acceptable. Proceed. */
And this code fragment demonstrates how a Windows Sockets DLL which supports only
version 1.1 performs the WSAStartup() negotiation:
/* Make sure that the version requested is >= 1.1. */
/* The low byte is the major version and the high */
/* byte is the minor version. */
if ( LOBYTE( wVersionRequested ) < 1 ||
( LOBYTE( wVersionRequested ) == 1 &&
HIBYTE( wVersionRequested ) < 1 ) {
return WSAVERNOTSUPPORTED;
}
/* Since we only support 1.1, set both wVersion and */
/* wHighVersion to 1.1. */
lpWsaData->wVersion = MAKEWORD( 1, 1 );
lpWsaData->wHighVersion = MAKEWORD( 1, 1 );
Once an application has made a successful WSAStartup() call, it may
proceed to make other Windows Sockets API calls as needed. When it has
finished using the services of the Windows Sockets DLL, the application must
call
WSACleanup()
in order to allow the DLL to free any resources allocated by the Windows
Sockets DLL for the application.
Details of the actual Windows Sockets implementation are described in the
WSAData structure defined as follows:
struct WSAData {
WORD wVersion;
WORD wHighVersion;
char szDescription[WSADESCRIPTION_LEN+1];
char szSystemStatus[WSASYSSTATUS_LEN+1];
unsigned short iMaxSockets;
unsigned short iMaxUdpDg;
char FAR * lpVendorInfo
};
The members of this structure are:
- wVersion
- The version of the Windows Sockets specification that the Windows Sockets
DLL expects the caller to use.
- wHighVersion
- The highest version of the Windows Sockets specification that this DLL can
support (also encoded as above). Normally this will be the same as wVersion.
- szDescription
- A null-terminated ASCII string into which the Windows Sockets DLL copies a
description of the Windows Sockets implementation, including vendor
identification. The text (up to 256 characters in length) may contain any
characters, but vendors are cautioned against including control and formatting
characters: the most likely use that an application will put this to is to
display it (possibly truncated) in a status message.
- szSystemStatus
- A null-terminated ASCII string into which the Windows Sockets DLL copies
relevant status or configuration information. The Windows Sockets DLL should
use this field only if the information might be useful to the user or support
staff: it should not be considered as an extension of the szDescription field.
- iMaxSockets
- The maximum number of sockets which a single process can potentially open.
A Windows Sockets implementation may provide a global pool of sockets for
allocation to any process; alternatively it may allocate per-process resources
for sockets. The number may well reflect the way in which the Windows Sockets
DLL or the networking software was configured. Application writers may use
this number as a crude indication of whether the Windows Sockets implementation
is usable by the application. For example, an X Windows server might check
iMaxSockets when first started: if it is less than 8, the application would
display an error message instructing the user to reconfigure the networking
software. (This is a situation in which the szSystemStatus text might be
used.) Obviously there is no guarantee that a particular application can
actually allocate iMaxSockets sockets, since there may be other Windows Sockets
applications in use.
- iMaxUdpDg
- The size in bytes of the largest UDP datagram that can be sent or received
by a Windows Sockets application. If the implementation imposes no limit,
iMaxUdpDg is zero. In many implementations of Berkeley sockets, there is an
implicit limit of 8192 bytes on UDP datagrams (which are fragmented if
necessary). A Windows Sockets implementation may impose a limit based, for
instance, on the allocation of fragment reassembly buffers. The minimum value
of iMaxUdpDg for a compliant Windows Sockets implementation is 512. Note that
regardless of the value of iMaxUdpDg, it is inadvisable to attempt to send a
broadcast datagram which is larger than the Maximum Transmission Unit
(MTU) for the network. (The Windows Sockets API does not provide a mechanism
to discover the MTU, but it must be no less than 512 bytes.)
- lpVendorInfo
- A far pointer to a vendor-specific data structure. The definition of this
structure (if supplied) is beyond the scope of this specification.
An application may call WSAStartup() more than once if it needs to
obtain the WSAData structure information more than once. However, the
wVersionRequired parameter is assumed to be the same on all calls to
WSAStartup(); that is, an application cannot change the version of
Windows Sockets it expects after the initial call to WSAStartup().
There must be one
WSACleanup()
call corresponding to every WSAStartup() call to allow third-party
DLLs to make use of a Windows Sockets DLL on behalf of an application. This
means, for example, that if an application calls WSAStartup() three
times, it must call
WSACleanup()
three times. The first two calls to
WSACleanup()
do nothing except decrement an internal counter; the final
WSACleanup()
call does all necessary resource deallocation for the task.
Return Value
WSAStartup() returns zero if successful. Otherwise
it returns one of the error codes listed below. Note that the normal mechanism
whereby the application calls
WSAGetLastError()
to determine the error code cannot be used, since the Windows Sockets DLL may
not have established the client data area where the "last error" information is
stored.
Notes For Windows Sockets Suppliers
Each Windows Sockets application must make a
WSAStartup() call before issuing any other Windows Sockets API calls.
This function can thus be utilized for initialization purposes.
Further issues are discussed in the notes for
WSACleanup().
Error Codes
- WSASYSNOTREADY
- Indicates that the underlying network subsystem is not ready
for network communication.
- WSAVERNOTSUPPORTED
- The version of Windows Sockets API support requested is not provided by
this particular Windows Sockets implementation.
- WSAEINVAL
- The Windows Sockets version specified by the application is not supported
by this DLL.
See Also
send(),
sendto(),
WSACleanup()
Description
Restore the default blocking hook function.
#include <winsock.h>
int PASCAL FAR WSAUnhookBlockingHook ( void );
Remarks
This function removes any previous blocking hook that has been
installed and reinstalls the default blocking mechanism.
WSAUnhookBlockingHook() will always install the default
mechanism, not the previous mechanism. If an application wish to nest
blocking hooks -- i.e. to establish a temporary blocking hook function and then
revert to the previous mechanism (whether the default or one established by an
earlier
WSASetBlockingHook())
- it must save and restore the value returned by
WSASetBlockingHook();
it cannot use WSAUnhookBlockingHook().
In multithreaded versions of Windows such as Windows NT, there is no default
blocking hook. Calling WSAUnhookBlockingHook() disables any blocking
hook installed by the application and any blocking calls made block the thread
which made the call.
Return Value
The return value is 0 if the operation was successful.
Otherwise the value SOCKET_ERROR is returned, and a specific error number may
be retrieved by calling
WSAGetLastError().
Error Codes
- WSAENOTINITIALISED
- A successful
WSAStartup() must occur before using this API.
See Also
WSASetBlockingHook()
The following is a list of possible error codes returned by the
WSAGetLastError()
call, along with their explanations. The error numbers are consistently set
across all Windows Sockets-compliant implementations.
Windows Sockets Berkeley Error Interpretation
----------------- -------------- ------- ----------------
WSAEINTR EINTR 10004 As in standard C
WSAEBADF EBADF 10009 As in standard C
WSEACCES EACCES 10013 As in standard C
WSAEFAULT EFAULT 10014 As in standard C
WSAEINVAL EINVAL 10022 As in standard C
WSAEMFILE EMFILE 10024 As in standard C
WSAEWOULDBLOCK EWOULDBLOCK 10035 As in BSD
WSAEINPROGRESS EINPROGRESS 10036 This error is returned
if any Windows Sockets
API function is called
while a blocking
function is in
progress.
WSAEALREADY EALREADY 10037 As in BSD
WSAENOTSOCK ENOTSOCK 10038 As in BSD
WSAEDESTADDRREQ EDESTADDRREQ 10039 As in BSD
WSAEMSGSIZE EMSGSIZE 10040 As in BSD
WSAEPROTOTYPE EPROTOTYPE 10041 As in BSD
WSAENOPROTOOPT ENOPROTOOPT 10042 As in BSD
WSAEPROTONOSUPPORT EPROTONOSUPPORT 10043 As in BSD
WSAESOCKTNOSUPPORT ESOCKTNOSUPPORT 10044 As in BSD
WSAEOPNOTSUPP EOPNOTSUPP 10045 As in BSD
WSAEPFNOSUPPORT EPFNOSUPPORT 10046 As in BSD
WSAEAFNOSUPPORT EAFNOSUPPORT 10047 As in BSD
WSAEADDRINUSE EADDRINUSE 10048 As in BSD
WSAEADDRNOTAVAIL EADDRNOTAVAIL 10049 As in BSD
WSAENETDOWN ENETDOWN 10050 As in BSD. This error
may be reported at any
time if the Windows
Sockets implementation
detects an underlying
failure.
WSAENETUNREACH ENETUNREACH 10051 As in BSD
WSAENETRESET ENETRESET 10052 As in BSD
WSAECONNABORTED ECONNABORTED 10053 As in BSD
WSAECONNRESET ECONNRESET 10054 As in BSD
WSAENOBUFS ENOBUFS 10055 As in BSD
WSAEISCONN EISCONN 10056 As in BSD
WSAENOTCONN ENOTCONN 10057 As in BSD
WSAESHUTDOWN ESHUTDOWN 10058 As in BSD
WSAETOOMANYREFS ETOOMANYREFS 10059 As in BSD
WSAETIMEDOUT ETIMEDOUT 10060 As in BSD
WSAECONNREFUSED ECONNREFUSED 10061 As in BSD
WSAELOOP ELOOP 10062 As in BSD
WSAENAMETOOLONG ENAMETOOLONG 10063 As in BSD
WSAEHOSTDOWN EHOSTDOWN 10064 As in BSD
WSAEHOSTUNREACH EHOSTUNREACH 10065 As in BSD
WSASYSNOTREADY 10091 Returned by WSAStartup()
indicating that the
network subsystem is
unusable.
WSAVERNOTSUPPORTED 10092 Returned by WSAStartup()
indicating that the
Windows Sockets DLL
cannot support this
app.
WSAENOTINITIALISED 10093 Returned by any
function except
WSAStartup()
indicating that a
successful WSAStartup()
has not yet been
performed.
WSAHOST_NOT_FOUND HOST_NOT_FOUND 11001 As in BSD.
WSATRY_AGAIN TRY_AGAIN 11002 As in BSD
WSANO_RECOVERY NO_RECOVERY 11003 As in BSD
WSANO_DATA NO_DATA 11004 As in BSD
The first set of definitions is present to resolve contentions between standard
C error codes which may be defined inconsistently between various C
compilers.
The second set of definitions provides Windows Sockets versions of regular
Berkeley Sockets error codes.
The third set of definitions consists of extended Windows Sockets-specific
error codes.
The fourth set of errors are returned by Windows Sockets
getXbyY()
and WSAAsyncGetXByY() functions, and correspond to the errors which in
Berkeley software would be returned in the h_errno variable. They
correspond to various failures which may be returned by the Domain Name
Service. If the Windows Sockets implementation does not use the DNS, it will
use the most appropriate code. In general, a Windows Sockets application
should interpret WSAHOST_NOT_FOUND and
WSANO_DATA as indicating that the key
(name, address, etc.) was not found, while
WSATRY_AGAIN and WSANO_RECOVERY
suggest that the name service itself is non-operational.
The error numbers are derived from the
winsock.h
header file, and are based on the fact that Windows Sockets error numbers are
computed by adding 10000 to the "normal" Berkeley error number.
Note that this table does not include all of the error codes defined in
winsock.h. This is because it includes only errors which might
reasonably be returned by a Windows Sockets implementation: winsock.h,
on the other hand, includes a full set of BSD definitions to ensure
compatibility with ported software.
Berkeley Header Files
Windows Sockets Header File -- winsock.h
A Windows Sockets supplier who provides a development kit to support the
development of Windows Sockets applications must supply a set of vestigial
header files with names that match a number of the header files in the Berkeley
software distribution. These files are provided for source code compatibility
only, and each consists of three lines:
#ifndef _WINSOCKAPI_
#include <winsock.h>
#endif
The header files provided for compatibility are:
- netdb.h
- arpa/inet.h
- sys/time.h
- sys/socket.h
- netinet/in.h
The file
winsock.h
contains all of the type and structure definitions, constants, macros, and
function prototypes used by the Windows Sockets specification. An application
writer may choose to ignore the compatibility headers and include
winsock.h in each source file.
The winsock.h header file includes a number of types and definitions
from the standard Windows header file windows.h. The windows.h
in the Windows 3.0 SDK (Software Developer's Kit) lacks a #include guard, so if
you need to include windows.h as well as winsock.h, you should
define the symbol _INC_WINDOWS before #including winsock.h, as follows:
#include <windows.h>
#define _INC_WINDOWS
#include <winsock.h>
Users
of the SDK for Windows 3.1 and later need not do this.
A Windows Sockets DLL vendor MUST NOT make any modifications to this
header file which could impact binary compatibility of Windows Sockets
applications. The constant values, function parameters and return codes, and
the like must remain consistent across all Windows Sockets DLL vendors.
/* WINSOCK.H--definitions to be used with the WINSOCK.DLL
*
* This header file corresponds to version 1.1 of the Windows Sockets specification.
*
* This file includes parts which are Copyright (c) 1982-1986 Regents
* of the University of California. All rights reserved. The
* Berkeley Software License Agreement specifies the terms and
* conditions for redistribution.
*/
#ifndef _WINSOCKAPI_
#define _WINSOCKAPI_
/*
* Pull in WINDOWS.H if necessary
*/
#ifndef _INC_WINDOWS
#include <windows.h>
#endif /* _INC_WINDOWS */
/*
* Basic system type definitions, taken from the BSD file sys/types.h.
*/
typedef unsigned char u_char;
typedef unsigned short u_short;
typedef unsigned int u_int;
typedef unsigned long u_long;
/*
* The new type to be used in all
* instances which refer to sockets.
*/
typedef u_int SOCKET;
/*
* Select uses arrays of SOCKETs. These macros manipulate such
* arrays. FD_SETSIZE may be defined by the user before including
* this file, but the default here should be >= 64.
*
* CAVEAT IMPLEMENTOR and USER: THESE MACROS AND TYPES MUST BE
* INCLUDED IN WINSOCK.H EXACTLY AS SHOWN HERE.
*/
#ifndef FD_SETSIZE
#define FD_SETSIZE 64
#endif /* FD_SETSIZE */
typedef struct fd_set {
u_short fd_count; /* how many are SET? */
SOCKET fd_array[FD_SETSIZE]; /* an array of SOCKETs */
} fd_set;
extern int PASCAL FAR __WSAFDIsSet(SOCKET, fd_set FAR *);
#define FD_CLR(fd, set) do { \
u_int __i; \
for (__i = 0; __i < ((fd_set FAR *)(set))->fd_count ; __i++) { \
if (((fd_set FAR *)(set))->fd_array[__i] == fd) { \
while (__i < ((fd_set FAR *)(set))->fd_count-1) { \
((fd_set FAR *)(set))->fd_array[__i] = \
((fd_set FAR *)(set))->fd_array[__i+1]; \
__i++; \
} \
((fd_set FAR *)(set))->fd_count--; \
break; \
} \
} \
} while(0)
#define FD_SET(fd, set) do { \
if (((fd_set FAR *)(set))->fd_count < FD_SETSIZE) \
((fd_set FAR *)(set))->fd_array[((fd_set FAR *)(set))->fd_count++]=fd;\
} while(0)
#define FD_ZERO(set) (((fd_set FAR *)(set))->fd_count=0)
#define FD_ISSET(fd, set) __WSAFDIsSet((SOCKET)fd, (fd_set FAR *)set)
/*
* Structure used in select() call, taken from the BSD file sys/time.h.
*/
struct timeval {
long tv_sec; /* seconds */
long tv_usec; /* and microseconds */
};
/*
* Operations on timevals.
*
* NB: timercmp does not work for >= or <=.
*/
#define timerisset(tvp) ((tvp)->tv_sec || (tvp)->tv_usec)
#define timercmp(tvp, uvp, cmp) \
((tvp)->tv_sec cmp (uvp)->tv_sec || \
(tvp)->tv_sec == (uvp)->tv_sec && (tvp)->tv_usec cmp (uvp)->tv_usec)
#define timerclear(tvp) (tvp)->tv_sec = (tvp)->tv_usec = 0
/*
* Commands for ioctlsocket(), taken from the BSD file fcntl.h.
*
*
* Ioctl's have the command encoded in the lower word,
* and the size of any in or out parameters in the upper
* word. The high 2 bits of the upper word are used
* to encode the in/out status of the parameter; for now
* we restrict parameters to at most 128 bytes.
*/
#define IOCPARM_MASK 0x7f /* parameters must be < 128 bytes */
#define IOC_VOID 0x20000000 /* no parameters */
#define IOC_OUT 0x40000000 /* copy out parameters */
#define IOC_IN 0x80000000 /* copy in parameters */
#define IOC_INOUT (IOC_IN|IOC_OUT)
/* 0x20000000 distinguishes new &
old ioctl's */
#define _IO(x,y) (IOC_VOID|(x<<8)|y)
#define _IOR(x,y,t) (IOC_OUT|(((long)sizeof(t)&IOCPARM_MASK)<<16)|(x<<8)|y)
#define _IOW(x,y,t) (IOC_IN|(((long)sizeof(t)&IOCPARM_MASK)<<16)|(x<<8)|y)
#define FIONREAD _IOR('f', 127, u_long) /* get # bytes to read */
#define FIONBIO _IOW('f', 126, u_long) /* set/clear non-blocking i/o */
#define FIOASYNC _IOW('f', 125, u_long) /* set/clear async i/o */
/* Socket I/O Controls */
#define SIOCSHIWAT _IOW('s', 0, u_long) /* set high watermark */
#define SIOCGHIWAT _IOR('s', 1, u_long) /* get high watermark */
#define SIOCSLOWAT _IOW('s', 2, u_long) /* set low watermark */
#define SIOCGLOWAT _IOR('s', 3, u_long) /* get low watermark */
#define SIOCATMARK _IOR('s', 7, u_long) /* at oob mark? */
/*
* Structures returned by network data base library, taken from the
* BSD file netdb.h. All addresses are supplied in host order, and
* returned in network order (suitable for use in system calls).
*/
struct hostent {
char FAR * h_name; /* official name of host */
char FAR * FAR * h_aliases; /* alias list */
short h_addrtype; /* host address type */
short h_length; /* length of address */
char FAR * FAR * h_addr_list; /* list of addresses */
#define h_addr h_addr_list[0] /* address, for backward compat */
};
/*
* It is assumed here that a network number
* fits in 32 bits.
*/
struct netent {
char FAR * n_name; /* official name of net */
char FAR * FAR * n_aliases; /* alias list */
short n_addrtype; /* net address type */
u_long n_net; /* network # */
};
struct servent {
char FAR * s_name; /* official service name */
char FAR * FAR * s_aliases; /* alias list */
short s_port; /* port # */
char FAR * s_proto; /* protocol to use */
};
struct protoent {
char FAR * p_name; /* official protocol name */
char FAR * FAR * p_aliases; /* alias list */
short p_proto; /* protocol # */
};
/*
* Constants and structures defined by the internet system,
* Per RFC 790, September 1981, taken from the BSD file netinet/in.h.
*/
/*
* Protocols
*/
#define IPPROTO_IP 0 /* dummy for IP */
#define IPPROTO_ICMP 1 /* control message protocol */
#define IPPROTO_GGP 2 /* gateway^2 (deprecated) */
#define IPPROTO_TCP 6 /* tcp */
#define IPPROTO_PUP 12 /* pup */
#define IPPROTO_UDP 17 /* user datagram protocol */
#define IPPROTO_IDP 22 /* xns idp */
#define IPPROTO_ND 77 /* UNOFFICIAL net disk proto */
#define IPPROTO_RAW 255 /* raw IP packet */
#define IPPROTO_MAX 256
/*
* Port/socket numbers: network standard functions
*/
#define IPPORT_ECHO 7
#define IPPORT_DISCARD 9
#define IPPORT_SYSTAT 11
#define IPPORT_DAYTIME 13
#define IPPORT_NETSTAT 15
#define IPPORT_FTP 21
#define IPPORT_TELNET 23
#define IPPORT_SMTP 25
#define IPPORT_TIMESERVER 37
#define IPPORT_NAMESERVER 42
#define IPPORT_WHOIS 43
#define IPPORT_MTP 57
/*
* Port/socket numbers: host specific functions
*/
#define IPPORT_TFTP 69
#define IPPORT_RJE 77
#define IPPORT_FINGER 79
#define IPPORT_TTYLINK 87
#define IPPORT_SUPDUP 95
/*
* UNIX TCP sockets
*/
#define IPPORT_EXECSERVER 512
#define IPPORT_LOGINSERVER 513
#define IPPORT_CMDSERVER 514
#define IPPORT_EFSSERVER 520
/*
* UNIX UDP sockets
*/
#define IPPORT_BIFFUDP 512
#define IPPORT_WHOSERVER 513
#define IPPORT_ROUTESERVER 520
/* 520+1 also used */
/*
* Ports < IPPORT_RESERVED are reserved for
* privileged processes (e.g. root).
*/
#define IPPORT_RESERVED 1024
/*
* Link numbers
*/
#define IMPLINK_IP 155
#define IMPLINK_LOWEXPER 156
#define IMPLINK_HIGHEXPER 158
/*
* Internet address (old style... should be updated)
*/
struct in_addr {
union {
struct { u_char s_b1,s_b2,s_b3,s_b4; } S_un_b;
struct { u_short s_w1,s_w2; } S_un_w;
u_long S_addr;
} S_un;
#define s_addr S_un.S_addr
/* can be used for most tcp & ip code */
#define s_host S_un.S_un_b.s_b2
/* host on imp */
#define s_net S_un.S_un_b.s_b1
/* network */
#define s_imp S_un.S_un_w.s_w2
/* imp */
#define s_impno S_un.S_un_b.s_b4
/* imp # */
#define s_lh S_un.S_un_b.s_b3
/* logical host */
};
/*
* Definitions of bits in internet address integers.
* On subnets, the decomposition of addresses to host and net parts
* is done according to subnet mask, not the masks here.
*/
#define IN_CLASSA(i) (((long)(i) & 0x80000000) == 0)
#define IN_CLASSA_NET 0xff000000
#define IN_CLASSA_NSHIFT 24
#define IN_CLASSA_HOST 0x00ffffff
#define IN_CLASSA_MAX 128
#define IN_CLASSB(i) (((long)(i) & 0xc0000000) == 0x80000000)
#define IN_CLASSB_NET 0xffff0000
#define IN_CLASSB_NSHIFT 16
#define IN_CLASSB_HOST 0x0000ffff
#define IN_CLASSB_MAX 65536
#define IN_CLASSC(i) (((long)(i) & 0xc0000000) == 0xc0000000)
#define IN_CLASSC_NET 0xffffff00
#define IN_CLASSC_NSHIFT 8
#define IN_CLASSC_HOST 0x000000ff
#define INADDR_ANY (u_long)0x00000000
#define INADDR_LOOPBACK 0x7f000001
#define INADDR_BROADCAST (u_long)0xffffffff
#define INADDR_NONE 0xffffffff
/*
* Socket address, internet style.
*/
struct sockaddr_in {
short sin_family;
u_short sin_port;
struct in_addr sin_addr;
char sin_zero[8];
};
#define WSADESCRIPTION_LEN 256
#define WSASYS_STATUS_LEN 128
typedef struct WSAData {
WORD wVersion;
WORD wHighVersion;
char szDescription[WSADESCRIPTION_LEN+1];
char szSystemStatus[WSASYS_STATUS_LEN+1];
unsigned short iMaxSockets;
unsigned short iMaxUdpDg;
char FAR * lpVendorInfo;
} WSADATA;
typedef WSADATA FAR *LPWSADATA;
/*
* Options for use with [gs]etsockopt at the IP level.
*/
#define IP_OPTIONS 1 /* set/get IP per-packet options */
/*
* Definitions related to sockets: types, address families, options,
* taken from the BSD file sys/socket.h.
*/
/*
* This is used instead of -1, since the
* SOCKET type is unsigned.
*/
#define INVALID_SOCKET (SOCKET)(~0)
#define SOCKET_ERROR (-1)
/*
* Types
*/
#define SOCK_STREAM 1 /* stream socket */
#define SOCK_DGRAM 2 /* datagram socket */
#define SOCK_RAW 3 /* raw-protocol interface */
#define SOCK_RDM 4 /* reliably-delivered message */
#define SOCK_SEQPACKET 5 /* sequenced packet stream */
/*
* Option flags per-socket.
*/
#define SO_DEBUG 0x0001 /* turn on debugging info recording */
#define SO_ACCEPTCONN 0x0002 /* socket has had listen() */
#define SO_REUSEADDR 0x0004 /* allow local address reuse */
#define SO_KEEPALIVE 0x0008 /* keep connections alive */
#define SO_DONTROUTE 0x0010 /* just use interface addresses */
#define SO_BROADCAST 0x0020 /* permit sending of broadcast msgs */
#define SO_USELOOPBACK 0x0040 /* bypass hardware when possible */
#define SO_LINGER 0x0080 /* linger on close if data present */
#define SO_OOBINLINE 0x0100 /* leave received OOB data in line */
#define SO_DONTLINGER (u_int)(~SO_LINGER)
/*
* Additional options.
*/
#define SO_SNDBUF 0x1001 /* send buffer size */
#define SO_RCVBUF 0x1002 /* receive buffer size */
#define SO_SNDLOWAT 0x1003 /* send low-water mark */
#define SO_RCVLOWAT 0x1004 /* receive low-water mark */
#define SO_SNDTIMEO 0x1005 /* send timeout */
#define SO_RCVTIMEO 0x1006 /* receive timeout */
#define SO_ERROR 0x1007 /* get error status and clear */
#define SO_TYPE 0x1008 /* get socket type */
/*
* TCP options.
*/
#define TCP_NODELAY 0x0001
/*
* Address families.
*/
#define AF_UNSPEC 0 /* unspecified */
#define AF_UNIX 1 /* local to host (pipes, portals) */
#define AF_INET 2 /* internetwork: UDP, TCP, etc. */
#define AF_IMPLINK 3 /* arpanet imp addresses */
#define AF_PUP 4 /* pup protocols: e.g. BSP */
#define AF_CHAOS 5 /* mit CHAOS protocols */
#define AF_NS 6 /* XEROX NS protocols */
#define AF_ISO 7 /* ISO protocols */
#define AF_OSI AF_ISO /* OSI is ISO */
#define AF_ECMA 8 /* european computer manufacturers */
#define AF_DATAKIT 9 /* datakit protocols */
#define AF_CCITT 10 /* CCITT protocols, X.25 etc */
#define AF_SNA 11 /* IBM SNA */
#define AF_DECnet 12 /* DECnet */
#define AF_DLI 13 /* Direct data link interface */
#define AF_LAT 14 /* LAT */
#define AF_HYLINK 15 /* NSC Hyperchannel */
#define AF_APPLETALK 16 /* AppleTalk */
#define AF_NETBIOS 17 /* NetBios-style addresses */
#define AF_MAX 18
/*
* Structure used by kernel to store most
* addresses.
*/
struct sockaddr {
u_short sa_family; /* address family */
char sa_data[14]; /* up to 14 bytes of direct address */
};
/*
* Structure used by kernel to pass protocol
* information in raw sockets.
*/
struct sockproto {
u_short sp_family; /* address family */
u_short sp_protocol; /* protocol */
};
/*
* Protocol families, same as address families for now.
*/
#define PF_UNSPEC AF_UNSPEC
#define PF_UNIX AF_UNIX
#define PF_INET AF_INET
#define PF_IMPLINK AF_IMPLINK
#define PF_PUP AF_PUP
#define PF_CHAOS AF_CHAOS
#define PF_NS AF_NS
#define PF_ISO AF_ISO
#define PF_OSI AF_OSI
#define PF_ECMA AF_ECMA
#define PF_DATAKIT AF_DATAKIT
#define PF_CCITT AF_CCITT
#define PF_SNA AF_SNA
#define PF_DECnet AF_DECnet
#define PF_DLI AF_DLI
#define PF_LAT AF_LAT
#define PF_HYLINK AF_HYLINK
#define PF_APPLETALK AF_APPLETALK
#define PF_MAX AF_MAX
/*
* Structure used for manipulating linger option.
*/
struct linger {
u_short l_onoff; /* option on/off */
u_short l_linger; /* linger time */
};
/*
* Level number for (get/set)sockopt() to apply to socket itself.
*/
#define SOL_SOCKET 0xffff /* options for socket level */
/*
* Maximum queue length specifiable by listen.
*/
#define SOMAXCONN 5
#define MSG_OOB 0x1 /* process out-of-band data */
#define MSG_PEEK 0x2 /* peek at incoming message */
#define MSG_DONTROUTE 0x4 /* send without using routing tables */
#define MSG_MAXIOVLEN 16
/*
* Define constant based on rfc883, used by gethostbyxxxx() calls.
*/
#define MAXGETHOSTSTRUCT 1024
/*
* Define flags to be used with the WSAAsyncSelect() call.
*/
#define FD_READ 0x01
#define FD_WRITE 0x02
#define FD_OOB 0x04
#define FD_ACCEPT 0x08
#define FD_CONNECT 0x10
#define FD_CLOSE 0x20
/*
* All Windows Sockets error constants are biased by WSABASEERR from
* the "normal"
*/
#define WSABASEERR 10000
/*
* Windows Sockets definitions of regular Microsoft C error constants
*/
#define WSAEINTR (WSABASEERR+4)
#define WSAEBADF (WSABASEERR+9)
#define WSAEACCES (WSABASEERR+13)
#define WSAEFAULT (WSABASEERR+14)
#define WSAEINVAL (WSABASEERR+22)
#define WSAEMFILE (WSABASEERR+24)
/*
* Windows Sockets definitions of regular Berkeley error constants
*/
#define WSAEWOULDBLOCK (WSABASEERR+35)
#define WSAEINPROGRESS (WSABASEERR+36)
#define WSAEALREADY (WSABASEERR+37)
#define WSAENOTSOCK (WSABASEERR+38)
#define WSAEDESTADDRREQ (WSABASEERR+39)
#define WSAEMSGSIZE (WSABASEERR+40)
#define WSAEPROTOTYPE (WSABASEERR+41)
#define WSAENOPROTOOPT (WSABASEERR+42)
#define WSAEPROTONOSUPPORT (WSABASEERR+43)
#define WSAESOCKTNOSUPPORT (WSABASEERR+44)
#define WSAEOPNOTSUPP (WSABASEERR+45)
#define WSAEPFNOSUPPORT (WSABASEERR+46)
#define WSAEAFNOSUPPORT (WSABASEERR+47)
#define WSAEADDRINUSE (WSABASEERR+48)
#define WSAEADDRNOTAVAIL (WSABASEERR+49)
#define WSAENETDOWN (WSABASEERR+50)
#define WSAENETUNREACH (WSABASEERR+51)
#define WSAENETRESET (WSABASEERR+52)
#define WSAECONNABORTED (WSABASEERR+53)
#define WSAECONNRESET (WSABASEERR+54)
#define WSAENOBUFS (WSABASEERR+55)
#define WSAEISCONN (WSABASEERR+56)
#define WSAENOTCONN (WSABASEERR+57)
#define WSAESHUTDOWN (WSABASEERR+58)
#define WSAETOOMANYREFS (WSABASEERR+59)
#define WSAETIMEDOUT (WSABASEERR+60)
#define WSAECONNREFUSED (WSABASEERR+61)
#define WSAELOOP (WSABASEERR+62)
#define WSAENAMETOOLONG (WSABASEERR+63)
#define WSAEHOSTDOWN (WSABASEERR+64)
#define WSAEHOSTUNREACH (WSABASEERR+65)
#define WSAENOTEMPTY (WSABASEERR+66)
#define WSAEPROCLIM (WSABASEERR+67)
#define WSAEUSERS (WSABASEERR+68)
#define WSAEDQUOT (WSABASEERR+69)
#define WSAESTALE (WSABASEERR+70)
#define WSAEREMOTE (WSABASEERR+71)
/*
* Extended Windows Sockets error constant definitions
*/
#define WSASYSNOTREADY (WSABASEERR+91)
#define WSAVERNOTSUPPORTED (WSABASEERR+92)
#define WSAENOTINITIALISED (WSABASEERR+93)
/*
* Error return codes from gethostbyname() and gethostbyaddr()
* (when using the resolver). Note that these errors are
* retrieved via WSAGetLastError() and must therefore follow
* the rules for avoiding clashes with error numbers from
* specific implementations or language run-time systems.
* For this reason the codes are based at WSABASEERR+1001.
* Note also that [WSA]NO_ADDRESS is defined only for
* compatibility purposes.
*/
#define h_errno WSAGetLastError()
/* Authoritative Answer: Host not found */
#define WSAHOST_NOT_FOUND (WSABASEERR+1001)
#define HOST_NOT_FOUND WSAHOST_NOT_FOUND
/* Non-Authoritative: Host not found, or SERVERFAIL */
#define WSATRY_AGAIN (WSABASEERR+1002)
#define TRY_AGAIN WSATRY_AGAIN
/* Non recoverable errors, FORMERR, REFUSED, NOTIMP */
#define WSANO_RECOVERY (WSABASEERR+1003)
#define NO_RECOVERY WSANO_RECOVERY
/* Valid name, no data record of requested type */
#define WSANO_DATA (WSABASEERR+1004)
#define NO_DATA WSANO_DATA
/* no address, look for MX record */
#define WSANO_ADDRESS
WSANO_DATA
#define NO_ADDRESS WSANO_ADDRESS
/*
* Windows Sockets errors redefined as regular Berkeley error constants
*/
#define EWOULDBLOCK WSAEWOULDBLOCK
#define EINPROGRESS WSAEINPROGRESS
#define EALREADY WSAEALREADY
#define ENOTSOCK WSAENOTSOCK
#define EDESTADDRREQ WSAEDESTADDRREQ
#define EMSGSIZE WSAEMSGSIZE
#define EPROTOTYPE WSAEPROTOTYPE
#define ENOPROTOOPT WSAENOPROTOOPT
#define EPROTONOSUPPORT WSAEPROTONOSUPPORT
#define ESOCKTNOSUPPORT WSAESOCKTNOSUPPORT
#define EOPNOTSUPP WSAEOPNOTSUPP
#define EPFNOSUPPORT WSAEPFNOSUPPORT
#define EAFNOSUPPORT WSAEAFNOSUPPORT
#define EADDRINUSE WSAEADDRINUSE
#define EADDRNOTAVAIL WSAEADDRNOTAVAIL
#define ENETDOWN WSAENETDOWN
#define ENETUNREACH WSAENETUNREACH
#define ENETRESET WSAENETRESET
#define ECONNABORTED WSAECONNABORTED
#define ECONNRESET WSAECONNRESET
#define ENOBUFS WSAENOBUFS
#define EISCONN WSAEISCONN
#define ENOTCONN WSAENOTCONN
#define ESHUTDOWN WSAESHUTDOWN
#define ETOOMANYREFS WSAETOOMANYREFS
#define ETIMEDOUT WSAETIMEDOUT
#define ECONNREFUSED WSAECONNREFUSED
#define ELOOP WSAELOOP
#define ENAMETOOLONG WSAENAMETOOLONG
#define EHOSTDOWN WSAEHOSTDOWN
#define EHOSTUNREACH WSAEHOSTUNREACH
#define ENOTEMPTY WSAENOTEMPTY
#define EPROCLIM WSAEPROCLIM
#define EUSERS WSAEUSERS
#define EDQUOT WSAEDQUOT
#define ESTALE WSAESTALE
#define EREMOTE WSAEREMOTE
/* Socket function prototypes */
#ifdef __cplusplus
extern "C" {
#endif
SOCKET PASCAL FAR accept (SOCKET s, struct sockaddr FAR *addr,
int FAR *addrlen);
int PASCAL FAR bind (SOCKET s, const struct sockaddr FAR *addr, int namelen);
int PASCAL FAR closesocket (SOCKET s);
int PASCAL FAR connect (SOCKET s, const struct sockaddr FAR *name, int namelen);
int PASCAL FAR ioctlsocket (SOCKET s, long cmd, u_long FAR *argp);
int PASCAL FAR getpeername (SOCKET s, struct sockaddr FAR *name,
int FAR * namelen);
int PASCAL FAR getsockname (SOCKET s, struct sockaddr FAR *name,
int FAR * namelen);
int PASCAL FAR getsockopt (SOCKET s, int level, int optname,
char FAR * optval, int FAR *optlen);
u_long PASCAL FAR htonl (u_long hostlong);
u_short PASCAL FAR htons (u_short hostshort);
unsigned long PASCAL FAR inet_addr (const char FAR * cp);
char FAR * PASCAL FAR inet_ntoa (struct in_addr in);
int PASCAL FAR listen (SOCKET s, int backlog);
u_long PASCAL FAR ntohl (u_long netlong);
u_short PASCAL FAR ntohs (u_short netshort);
int PASCAL FAR recv (SOCKET s, char FAR * buf, int len, int flags);
int PASCAL FAR recvfrom (SOCKET s, char FAR * buf, int len, int flags,
struct sockaddr FAR *from, int FAR * fromlen);
int PASCAL FAR select (int nfds, fd_set FAR *readfds, fd_set FAR *writefds,
fd_set FAR *exceptfds, const struct timeval FAR *timeout);
int PASCAL FAR send (SOCKET s, const char FAR * buf, int len, int flags);
int PASCAL FAR sendto (SOCKET s, const char FAR * buf, int len, int flags,
const struct sockaddr FAR *to, int tolen);
int PASCAL FAR setsockopt (SOCKET s, int level, int optname,
const char FAR * optval, int optlen);
int PASCAL FAR shutdown (SOCKET s, int how);
SOCKET PASCAL FAR socket (int af, int type, int protocol);
/* Database function prototypes */
struct hostent FAR * PASCAL FAR gethostbyaddr(const char FAR * addr,
int len, int type);
struct hostent FAR * PASCAL FAR gethostbyname(const char FAR * name);
int PASCAL FAR gethostname (char FAR * name, int namelen);
struct servent FAR * PASCAL FAR getservbyport(int port, const char FAR * proto);
struct servent FAR * PASCAL FAR getservbyname(const char FAR * name,
const char FAR * proto);
struct protoent FAR * PASCAL FAR getprotobynumber(int proto);
struct protoent FAR * PASCAL FAR getprotobyname(const char FAR * name);
/* Microsoft Windows Extension function prototypes */
int PASCAL FAR WSAStartup(WORD wVersionRequired, LPWSADATA lpWSAData);
int PASCAL FAR WSACleanup(void);
void PASCAL FAR WSASetLastError(int iError);
int PASCAL FAR WSAGetLastError(void);
BOOL PASCAL FAR WSAIsBlocking(void);
int PASCAL FAR WSAUnhookBlockingHook(void);
FARPROC PASCAL FAR WSASetBlockingHook(FARPROC lpBlockFunc);
int PASCAL FAR WSACancelBlockingCall(void);
HANDLE PASCAL FAR WSAAsyncGetServByName(HWND hWnd, u_int wMsg,
const char FAR * name,
const char FAR * proto,
char FAR * buf, int buflen);
HANDLE PASCAL FAR WSAAsyncGetServByPort(HWND hWnd, u_int wMsg, int port,
const char FAR * proto, char FAR * buf,
int buflen);
HANDLE PASCAL FAR WSAAsyncGetProtoByName(HWND hWnd, u_int wMsg,
const char FAR * name, char FAR * buf,
int buflen);
HANDLE PASCAL FAR WSAAsyncGetProtoByNumber(HWND hWnd, u_int wMsg,
int number, char FAR * buf,
int buflen);
HANDLE PASCAL FAR WSAAsyncGetHostByName(HWND hWnd, u_int wMsg,
const char FAR * name, char FAR * buf,
int buflen);
HANDLE PASCAL FAR WSAAsyncGetHostByAddr(HWND hWnd, u_int wMsg,
const char FAR * addr, int len, int type,
const char FAR * buf, int buflen);
int PASCAL FAR WSACancelAsyncRequest(HANDLE hAsyncTaskHandle);
int PASCAL FAR WSAAsyncSelect(SOCKET s, HWND hWnd, u_int wMsg,
long lEvent);
#ifdef __cplusplus
}
#endif
/* Microsoft Windows Extended data types */
typedef struct sockaddr SOCKADDR;
typedef struct sockaddr *PSOCKADDR;
typedef struct sockaddr FAR *LPSOCKADDR;
typedef struct sockaddr_in SOCKADDR_IN;
typedef struct sockaddr_in *PSOCKADDR_IN;
typedef struct sockaddr_in FAR *LPSOCKADDR_IN;
typedef struct linger LINGER;
typedef struct linger *PLINGER;
typedef struct linger FAR *LPLINGER;
typedef struct in_addr IN_ADDR;
typedef struct in_addr *PIN_ADDR;
typedef struct in_addr FAR *LPIN_ADDR;
typedef struct fd_set FD_SET;
typedef struct fd_set *PFD_SET;
typedef struct fd_set FAR *LPFD_SET;
typedef struct hostent HOSTENT;
typedef struct hostent *PHOSTENT;
typedef struct hostent FAR *LPHOSTENT;
typedef struct servent SERVENT;
typedef struct servent *PSERVENT;
typedef struct servent FAR *LPSERVENT;
typedef struct protoent PROTOENT;
typedef struct protoent *PPROTOENT;
typedef struct protoent FAR *LPPROTOENT;
typedef struct timeval TIMEVAL;
typedef struct timeval *PTIMEVAL;
typedef struct timeval FAR *LPTIMEVAL;
/*
* Windows message parameter composition and decomposition
* macros.
*
* WSAMAKEASYNCREPLY is intended for use by the Windows Sockets implementation
* when constructing the response to a WSAAsyncGetXByY() routine.
*/
#define WSAMAKEASYNCREPLY(buflen,error) MAKELONG(buflen,error)
/*
* WSAMAKESELECTREPLY is intended for use by the Windows Sockets implementation
* when constructing the response to WSAAsyncSelect().
*/
#define WSAMAKESELECTREPLY(event,error) MAKELONG(event,error)
/*
* WSAGETASYNCBUFLEN is intended for use by the Windows Sockets application
* to extract the buffer length from the lParam in the response
* to a WSAGetXByY().
*/
#define WSAGETASYNCBUFLEN(lParam) LOWORD(lParam)
/*
* WSAGETASYNCERROR is intended for use by the Windows Sockets application
* to extract the error code from the lParam in the response
* to a WSAGetXByY().
*/
#define WSAGETASYNCERROR(lParam) HIWORD(lParam)
/*
* WSAGETSELECTEVENT is intended for use by the Windows Sockets application
* to extract the event code from the lParam in the response
* to a WSAAsyncSelect().
*/
#define WSAGETSELECTEVENT(lParam) LOWORD(lParam)
/*
* WSAGETSELECTERROR is intended for use by the Windows Sockets application
* to extract the error code from the lParam in the response
* to a WSAAsyncSelect().
*/
#define WSAGETSELECTERROR(lParam) HIWORD(lParam)
#endif /* _WINSOCKAPI_ */
Introduction
Windows Sockets Components
Multithreadedness and blocking routines.
Database Files
FD_ISSET
Error Codes
DLL Ordinal Numbers
Validation Suite
A Windows Sockets implementation must implement ALL the functionality described
in the Windows Sockets documentation. Validation of compliance is discussed in
Validation
Suite.
Windows Sockets Version 1.1 implementations must support both TCP and UDP type
sockets. An implementation may support raw sockets (of type SOCK_RAW), but
their use is deprecated.
Certain APIs documented above have special notes for Windows Sockets
implementors. A Windows Sockets implementation should pay special attention to
conforming to the API as documented. The Special Notes are provided for
assistance and clarification.
The Windows Sockets development components for use by Windows Sockets
application developers will be provided by each Windows Sockets supplier.
These Windows Sockets development components are:
Component Description
------------------------------- -----------------------------------------------
Windows Sockets Documentation This document
WINSOCK.LIB file Windows Sockets API Import Library
WINSOCK.H file Windows Sockets Header File
NETDB.H file Berkeley Compatible Header File
ARPA/INET.H file Berkeley Compatible Header File
SYS/TIME.H file Berkeley Compatible Header File
SYS/SOCKET.H file Berkeley Compatible Header File
NETINET/IN.H file Berkeley Compatible Header File
The run time component provided by each Windows Sockets supplier is:
Component Description
------------------------------- -----------------------------------------------
WINSOCK.DLL The Windows Sockets API implementation DLL
Data areas returned by, for example, the
getXbyY()
routines MUST be on a per thread basis.
Note that an application MUST be prevented from making multiple nested Windows
Sockets function calls. Only one outstanding function call will be allowed for
a particular task. Any Windows Sockets call performed when an existing
blocking call is already outstanding will fail with an error code of
WSAEINPROGRESS.
There are two exceptions to this restriction:
WSACancelBlockingCall()
and
WSAIsBlocking()
may be called at any time. Windows Sockets suppliers should note that although
preliminary drafts of this specification indicated that the restriction only
applied to blocking function calls, and that it would be permissible to make
non-blocking calls while a blocking call was in progress, this is no longer
true.
Regarding the implementation of blocking routines, the solution in Windows
Sockets is to simulate the blocking mechanism by having each routine call
PeekMessage() as it waits for the completion of its operation. In anticipation
of this, the function
WSASetBlockingHook()
is provided to allow the programmer to define a special routine to be called
instead of the default PeekMessage() loop. The blocking hook functions are
discussed in more detail in
WSASetBlockingHook().
The database routines in the
getXbyY()
family (gethostbyaddr(), etc.) were originally designed (in the first
Berkeley UNIX releases) as mechanisms for looking up information in text
databases. A Windows Sockets supplier may choose to employ local files OR a
name service to provide some or all of this information. If local files exist,
the format of the files must be identical to that used in BSD UNIX, allowing
for the differences in text file formats.
It is necessary to implement the FD_ISSET Berkeley macro using a supporting
function: __WSAFDIsSet(). It is the responsibility of a Windows Sockets
implementation to make this available as part of the Windows Sockets API.
Unlike the other functions exported by a Windows Sockets DLL, however, this
function is not intended to be invoked directly by Windows Sockets
applications: it should be used only to support the FD_ISSET macro. The source
code for this function is listed below:
int FAR
__WSAFDIsSet(SOCKET fd, fd_set FAR *set)
{
int i = set->count;
while (i--)
if (set->fd_array[i] == fd)
return 1;
return 0;
}
In order to avoid conflict between various compiler environments Windows
Sockets implementations MUST return the error codes listed in the API
specification, using the manifest constants beginning with "WSA". The
Berkeley-compatible error code definitions are provided solely for
compatibility purposes for applications which are being ported from other
platforms.
The winsock.def file for use by every Windows Sockets implementation is
as follows. Ordinal values starting at 1000 are reserved for Windows Sockets
implementors to use for exporting private interfaces to their DLLs. A Windows
Sockets implementation must not use any ordinals 999 and below except for those
APIs listed below. An application which wishes to work with any Windows
Sockets DLL must use only those routines listed below; using a private export
makes an application dependent on a particular Windows Sockets
implementation.
;
; File: winsock.def
; System: MS-Windows 3.x
; Summary: Module definition file for Windows Sockets DLL.
;
LIBRARY WINSOCK ; Application's module name
DESCRIPTION 'BSD Socket API for Windows'
EXETYPE WINDOWS ; required for all windows applications
STUB 'WINSTUB.EXE' ; generates error message if application
; is run without Windows
;CODE can be FIXED in memory because of potential upcalls
CODE PRELOAD FIXED
;DATA must be SINGLE and at a FIXED location since this is a DLL
DATA PRELOAD FIXED SINGLE
HEAPSIZE 1024
STACKSIZE 16384
; All functions that will be called by any Windows routine
; must be exported. Any additional exports beyond those defined
; here must have ordinal numbers 1000 or above.
EXPORTS
accept @1
bind @2
closesocket @3
connect @4
getpeername @5
getsockname @6
getsockopt @7
htonl @8
htons @9
inet_addr @10
inet_ntoa @11
ioctlsocket @12
listen @13
ntohl @14
ntohs @15
recv @16
recvfrom @17
select @18
send @19
sendto @20
setsockopt @21
shutdown @22
socket @23
gethostbyaddr @51
gethostbyname @52
getprotobyname @53
getprotobynumber @54
getservbyname @55
getservbyport @56
gethostname @57
WSAAsyncSelect @101
WSAAsyncGetHostByAddr @102
WSAAsyncGetHostByName @103
WSAAsyncGetProtoByNumber @104
WSAAsyncGetProtoByName @105
WSAAsyncGetServByPort @106
WSAAsyncGetServByName @107
WSACancelAsyncRequest @108
WSASetBlockingHook @109
WSAUnhookBlockingHook @110
WSAGetLastError @111
WSASetLastError @112
WSACancelBlockingCall @113
WSAIsBlocking @114
WSAStartup @115
WSACleanup @116
__WSAFDIsSet @151
WEP @500 RESIDENTNAME
;eof
The Windows Sockets API Tester (WSAT) to ensure Windows Sockets compatibility
between Windows Sockets DLL implementations is currently in beta test. This
beta version includes functionality testing of the Windows Sockets interface
and is supported by a comprehensive scripting language. The final version of
WSAT will be available in Spring 1993. If you wish to receive the tester or
more information on the beta, send email to
wsat@microsoft.com.
This specification is intended to cover the Windows Sockets interface to TCP/IP
in detail. Many details of TCP/IP and Windows, however, are intentionally
omitted in the interest of brevity, and this specification often assumes
background knowledge of these topics. For more information, the following
references may be helpful:
Braden, R.[1989], RFC 1122, Requirements for Internet Hosts--Communication
Layers, Internet Engineering Task Force.
Comer, D. [1991], Internetworking with TCP/IP Volume I: Principles,
Protocols, and Architecture, Prentice Hall, Englewood Cliffs, New Jersey.
Comer, D. and Stevens, D. [1991], Internetworking with TCP/IP Volume II:
Design, Implementation, and Internals, Prentice Hall, Englewood Cliffs, New
Jersey.
Comer, D. and Stevens, D. [1991], Internetworking with TCP/IP Volume III:
Client-Server Programming and Applications, Prentice Hall, Englewood
Cliffs, New Jersey.
Leffler, S. et al., An Advanced 4.3BSD Interprocess Communication
Tutorial.
Petzold, C. [1992], Programming Windows 3.1, Microsoft Press, Redmond,
Washington.
Stevens, W.R. [1990], Unix Network Programming, Prentice Hall, Englewood
Cliffs, New Jersey.
The Windows Sockets project had its origins in a Birds Of A Feather session
held at Interop '91 in San Jose on October 10, 1991. A committee was
established, and an intensive debate via email resulted in the creation of a
first draft specification, which was largely based on submissions from JSB and
NetManage. This draft, and issues arising from it, were debated at a committee
meeting hosted by Microsoft in Redmond, WA on December 9, 1991. Following
further email discussions, a working group was established to develop the
specification into its current form.
The following people participated in the process as committee members, in
working meetings, or in email review. The authors would like to thank everyone
who participated in any way, and apologize in advance if we have omitted
anyone.
Martin Hall (Moderator) JSB Corporation martinh@jsbus.com
Mark Towfiq (Coordinator) Microdyne Corporation towfiq@microdyne.com
Geoff Arnold Sun Microsystems, Inc. geoff@east.sun.com
Alistair Banks Microsoft alistair@microsoft.com
Carl Beame Beame & Whiteside beame@mcmaster,ca
David Beaver Microsoft dbeaver@microsoft.com
Amatzia BenArtzi NetManage, Inc. amatzia@netmanage.com
Mark Beyer Ungermann-Bass mbeyer@ub.com
James Van Bokkelen FTP Software jbvb@ftp.com
Nelson Bolyard Silicon Graphics, Inc. nelson@sgi.com
Pat Bonner Hewlett-Packard p_bonner@cnd.hp.com
Isaac Chan Microsoft isaacc@microsoft.com
Nestor Fesas Hughes LAN Systems nestor@hls.com
Gary Gere Gupta ggere@gupta.com
Bill Hayes Hewlett-Packard billh@hpchdpc.cnd.hp.com
Hoek Law Citicorp law@dcc.tti.com
Paul Hill MIT pbh@athena.mit.edu
Graeme Le Roux Moresdawn P/L -
Terry Lister Hewlett-Packard tel@cnd.hp.com
Lee Murach Network Research lee@nrc.com
David Pool Spry, Inc. dave@spry.com
Brad Rice Age rice@age.com
Allen Rochkind 3Com -
Henry Sanders Microsoft henrysa@microsoft.com
David Treadwell Microsoft davidtr@microsoft.com
Miles Wu Wollongong wu@twg.com
Boris Yanovsky NetManage, Inc. boris@netmanage.com
J Allard Microsoft Corporation jallard@microsoft.com
The copyright for the Windows Sockets specification is owned by the
specification authors listed on the title page. Permission is granted to
redistribute this specification in any form, provided that the contents of the
specification are not modified. Windows Sockets implementors are encouraged to
include this specification with their product documentation.
The Windows Sockets logo on the title page of this document is meant for use on
both Windows Sockets implementations and for applications that use the Windows
Sockets interface. Use of the logo is encouraged on packaging, documentation,
collateral, and advertising. The logo is available on SunSite.UNC.Edu
in /pub/micro/pc-stuff/ms-windows/winsock/winsock-1.1 as winsock.bmp. The
suggested color for the logo's title bar is blue, the electrical socket grey,
and the text and outline black.
(by Alistair Banks, Microsoft Corporation)
We thought we'd do a "Wind Sock" at one stage--but you try to get that into
32x32 bits! It would have had to look wavy and colorful, and... well, it just
didn't work. Also, our graphics designers have "opinions" about the icons truly
representing what they are--people would have thought this was "The colorful
wavy tube specification 1.0!"
I tried to explain "API" "Programming Interface" to the artist--we ended up
with toolbox icons with little flying windows.
Then we came to realise that we should be going after the shortened form of the
name, rather the name in full... Windows Sockets... And so we went for that --
so she drew (now remember I'm English and you're probably American) "Windows
Spanner", a.k.a. a socket wrench. In the U.S. you'd have been talking about
the "Windows Socket spec" OK, but in England that would have been translatated
as "Windows Spanner Spec 1.0" -- so we went to Electrical sockets -- well the
first ones came out looking like "Windows Pignose Spec 1.0"!!!!
So how do you use 32x32, get an international electrical socket! You take the
square type (American & English OK, Europe & Australia are too
rounded)--you choose the American one, because it's on the wall in front of you
(and it's more compact (but less safe, IMHO) and then you turn it upside down,
thereby compromising its nationality!
[IMHO = "In My Humble Opinion"--ed.]