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

WSANOTINITIALISED

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()

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