shutdown()

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

WSANOTINITIALISED

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()

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