The socket function creates a socket that is bound to a specific service provider.
afAddress family specification.
Type specification for the new socket.
The following are the only two type specifications supported for WindowsSockets 1.1: Type Explanation
SOCK_STREAM Provides sequenced, reliable, two-way, connection-based byte streams with an OOB data transmission mechanism. Uses TCPfor the Internet address family.
SOCK_DGRAM Supports datagrams, which are connectionless, unreliable buffers of a fixed(typically small) maximum length. Uses UDPfor the Internet address family.
In Windows Sockets 2, many new socket types will be introduced and no longer need to bespecified, since an application can dynamically discover the attributes of each available transport protocol through the WSAEnumProtocols function. Socket type definitions appear in Winsock2.h, which will be periodically updated as new socket types, address families, and protocols are defined.
Protocol to be used with the socket that is specific to the indicated address family.
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 can be retrieved by calling WSAGetLastError.
Error code Meaning
WSANOTINITIALISED A successful WSAStartupcall must occur before using this function.
WSAENETDOWN The network subsystem or the associated service provider has failed.
WSAEAFNOSUPPORT The specified address family is not supported.
WSAEINPROGRESS A blocking Windows Sockets 1.1 call is in progress, or the service provider is still processing a callback function.
WSAEMFILE No moresocket 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.
The socket function causes a socket descriptor and any related resources to be allocated and bound to a specific transport-service provider. Windows Sockets will utilize the first available service provider that supports the requested combination of address family, socket type and protocol parameters. The socket that is created will have the overlapped attribute as a default. For Microsoft operating systems, the Microsoft-specific socket option, SO_OPENTYPE, defined in Mswsock.h can affect this default. See Microsoft-specific documentation for a detailed description of SO_OPENTYPE.
Sockets without the overlapped attribute can be created by using WSASocket. All functions that allow overlapped operation (WSASend, WSARecv,WSASendTo, WSARecvFrom, and WSAIoctl) also support nonoverlapped usage on an overlapped socket if the values for parameters related to overlapped operation are NULL.
Whenselecting a protocol and its supporting service provider this procedurewill only choose a base protocol or a protocol chain, not a protocol layer by itself. Unchained protocol layers are not considered to have partial matches on type or af either. That is, they do not lead to an error code of WSAEAFNOSUPPORT or WSAEPROTONOSUPPORT if no suitable protocol is found.
Important The manifest constant AF_UNSPEC continues to be defined in the header file but its use is strongly discouraged, as this can cause ambiguity in interpreting the value of the protocol parameter.
Connection-oriented sockets such as SOCK_STREAM provide full-duplex connections, and must be in a connectedstate before any data can be sent or received on it. A connection to another socket is created with a connect call. Onceconnected, data can be transferred using send and recv calls. When a session has been completed, a closesocket must be performed.
The communications protocols used to implementa reliable, connection-oriented socket 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.
Connectionless, message-oriented sockets allow sending and receiving of datagrams to and from arbitrary peersusing sendto and recvfrom. If such a socket is connected to a specific peer, datagrams can be sent to that peer using send and can be received only from this peer using recv.
Support for sockets with type SOCK_RAW is not required, but service providers are encouraged to support raw sockets as practicable.
Notes for IrDA Sockets
The Af_irda.h header file must be explicitly included.
OnlySOCK_STREAM is supported; the SOCK_DGRAM type is not supported by IrDA.
The protocol parameter is always set to 0 for IrDA.
Note On Windows NT, raw socket support requires administrative privileges.
Windows NT/2000/XP: Included in Windows NT 3.1 and later.
Windows 95/98/Me: Included in Windows 95 and later.
Header: Declared in Winsock2.h.
Library: Use Ws2_32.lib.
Windows Sockets Programming Considerations Overview, Socket Functions, accept, bind, connect, getsockname, getsockopt, ioctlsocket, listen, recv, recvfrom, select, send, sendto, setsockopt, shutdown, WSASocket