The Windows Sockets WSASocket function creates a socket that is bound to a specific transport service provider, and optionally creates and/or joins a socket group.
SOCKET WSASocket (
int af,
int type,
int protocol,
LPWSAPROTOCOL_INFO lpProtocolInfo,
GROUP g,
DWORD dwFlags
);
The WSASocket function causes a socket descriptor and any related resources to be allocated and associated with a transport service provider. By default, the socket will not have an overlapped attribute. If lpProtocolInfo is NULL, the WS2_32.DLL uses the first three parameters (af, type, protocol) to determine which service provider is used by selecting the first transport provider able to support the stipulated address family, socket type and protocol values. If the lpProtocolInfo is not NULL, the socket will be bound to the provider associated with the indicated WSAPROTOCOL_INFO structure. In this instance, the application can supply the manifest constant FROM_PROTOCOL_INFO as the value for any of af, type or protocol. This indicates that the corresponding values from the indicated WSAPROTOCOL_INFO structure (iAddressFamily, iSocketType, iProtocol) are to be assumed. In any case, the values supplied for af, type and protocol are supplied unmodified to the transport service provider.
When selecting a protocol and its supporting service provider based on af, type and protocol, this procedure will 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.
Note 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.
Reserved for future use with socket groups. Parameter g is used to indicate the appropriate actions on socket groups:
For unconstrained groups, any set of sockets can be grouped together as long as they are supported by a single service provider. A constrained socket group can consist only of connection-oriented sockets, and requires that connections on all grouped sockets be to the same address on the same host. For newly created socket groups, the new group ID can be retrieved by using getsockopt with option SO_GROUP_ID, if this operation completes successfully. A socket group and its associated ID remain valid until the last socket belonging to this socket group is closed. Socket group IDs are unique across all processes for a given service provider.
The dwFlags parameter can be used to specify the attributes of the socket by or-ing any of the following Flags:
| Flag | Meaning |
|---|---|
| WSA_FLAG_OVERLAPPED | This flag causes an overlapped socket to be created. Overlapped sockets can utilize WSASend, WSASendTo, WSARecv, WSARecvFrom and WSAIoctl for overlapped I/O operations, which allows multiple these operations to be initiated and in progress simultaneously. All functions that allow overlapped operation (WSASend, WSARecv,WSASendTo, WSARecvFrom, WSAIoctl) also support non-overlapped usage on an overlapped socket if the values for parameters related to overlapped operation are NULL. |
| WSA_FLAG_MULTIPOINT_C_ROOT | Indicates that the socket created will be a c_root in a multipoint session. Only allowed if a rooted control plane is indicated in the protocol's WSAPROTOCOL_INFO structure. Refer to Multipoint and Multicast Semantics for additional information. |
| WSA_FLAG_MULTIPOINT_C_LEAF | Indicates that the socket created will be a c_leaf in a multicast session. Only allowed if XP1_SUPPORT_MULTIPOINT is indicated in the protocol's WSAPROTOCOL_INFO structure. Refer to Multipoint and Multicast Semantics for additional information. |
| WSA_FLAG_MULTIPOINT_D_ROOT | Indicates that the socket created will be a d_root in a multipoint session. Only allowed if a rooted data plane is indicated in the protocol's WSAPROTOCOL_INFO structure. Refer to Multipoint and Multicast Semantics for additional information. |
| WSA_FLAG_MULTIPOINT_D_LEAF | Indicates that the socket created will be a d_leaf in a multipoint session. Only allowed if XP1_SUPPORT_MULTIPOINT is indicated in the protocol's WSAPROTOCOL_INFO structure. Refer to Multipoint and Multicast Semantics for additional information. |
Important For multipoint sockets, exactly one of WSA_FLAG_MULTIPOINT_C_ROOT or WSA_FLAG_MULTIPOINT_C_LEAF must be specified, and exactly one of WSA_FLAG_MULTIPOINT_D_ROOT or WSA_FLAG_MULTIPOINT_D_LEAF must be specified. Refer to Multipoint and Multicast Semantics for additional information.
Connection-oriented sockets such as SOCK_STREAM provide full-duplex connections, and must be in a connected state before any data can be sent or received on them. A connection to another socket is created with a connect/WSAConnect call. Once connected, data can be transferred using send/WSASend and recv/WSARecv calls. When a session has been completed, a closesocket must be performed.
The communications protocols used to implement a 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 peers using sendto/WSASendTo and recvfrom/WSARecvFrom. If such a socket is connected to a specific peer, datagrams can be sent to that peer using send/WSASend and can be received from (only) this peer using recv/WSARecv.
Support for sockets with type RAW is not required, but service providers are encourages to support raw sockets whenever it makes sense to do so.
If no error occurs, WSASocket 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.
| WSANOTINITIALISED | A successful WSAStartup must occur before using this function. |
| WSAENETDOWN | The network subsystem 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 more socket 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. |
| WSAEINVAL | The parameter g specified is not valid, or the WSAPROTOCOL_INFO structure that lpProtocolInfo points to is incomplete, the contents are invalid or the WSAPROTOCOL_INFO structurehas already been used in an earlier duplicate socket operation. |
| WSAEFAULT | lpProtocolInfo argument is not in a valid part of the process address space. |
| WSAINVALIDPROVIDER | The service provider returned a version other than 2.2. |
| WSAINVALIDPROCTABLE | The service provider returned an invalid or incomplete procedure table to the WSPStartup. |
Windows NT: Yes
Windows: Yes
Windows CE: Unsupported.
Header: Declared in winsock2.h.
Import Library: Link with ws2_32.lib.
accept, bind, connect, getsockname, getsockopt, ioctlsocket, listen, recv, recvfrom, select, send, sendto, setsockopt, shutdown