shutdown function (winsock.h)

The shutdown function disables sends or receives on a socket.

int shutdown(
  [in] SOCKET s,
  [in] int    how
);

[in] s

A descriptor identifying a socket.

[in] how

A flag that describes what types of operation will no longer be allowed. Possible values for this flag are listed in the Winsock2.h header file.

If no error occurs, shutdown returns zero. Otherwise, a value of SOCKET_ERROR is returned, and a specific error code can be retrieved by calling WSAGetLastError.

The shutdown function is used on all types of sockets to disable reception, transmission, or both.

If the how parameter is SD_RECEIVE, subsequent calls to the recv function on the socket will be disallowed. This has no effect on the lower protocol layers. For TCP sockets, if there is still data queued on the socket waiting to be received, or data arrives subsequently, the connection is reset, since the data cannot be delivered to the user. For UDP sockets, incoming datagrams are accepted and queued. In no case will an ICMP error packet be generated.

If the how parameter is SD_SEND, subsequent calls to the send function are disallowed. For TCP sockets, a FIN will be sent after all data is sent and acknowledged by the receiver.

Setting how to SD_BOTH disables both sends and receives as described above.

The shutdown function does not close the socket. Any resources attached to the socket will not be freed until closesocket is invoked.

To assure that all data is sent and received on a connected socket before it is closed, an application should use shutdown to close connection before calling closesocket. One method to wait for notification that the remote end has sent all its data and initiated a graceful disconnect uses the WSAEventSelect function as follows :

1. Call WSAEventSelect to register for FD_CLOSE notification.
2. Call shutdown with how=SD_SEND.
3. When FD_CLOSE received, call the recv or WSARecv until the function completes with success and indicates that zero bytes were received. If SOCKET_ERROR is returned, then the graceful disconnect is not possible.
4. Call closesocket.

1. Call shutdown with how=SD_SEND.
2. Call recv or WSARecv until the function completes with success and indicates zero bytes were received. If SOCKET_ERROR is returned, then the graceful disconnect is not possible.
3. Call closesocket.

For more information, see the section on Graceful Shutdown, Linger Options, and Socket Closure.

Once the shutdown function is called to disable send, receive, or both, there is no method to re-enable send or receive for the existing socket connection.

An application should not rely on being able to reuse a socket after it has been shut down. In particular, a Windows Sockets provider is not required to support the use of connect on a socket that has been shut down.

If an application wants to reuse a socket, then the DisconnectEx function should be called with the dwFlags parameter set to TF_REUSE_SOCKET to close a connection on a socket and prepare the socket handle to be reused. When the DisconnectEx request completes, the socket handle can be passed to the AcceptEx or ConnectEx function.

If an application wants to reuse a socket, the TransmitFile or TransmitPackets functions can be called with the dwFlags parameter set with TF_DISCONNECT and TF_REUSE_SOCKET to disconnect after all the data has been queued for transmission and prepare the socket handle to be reused. When the TransmitFile request completes, the socket handle can be passed to the function call previously used to establish the connection, such as AcceptEx or ConnectEx. When the TransmitPackets function completes, the socket handle can be passed to the AcceptEx function.

Windows Phone 8: This function is supported for Windows Phone Store apps on Windows Phone 8 and later.

Windows 8.1 and Windows Server 2012 R2: This function is supported for Windows Store apps on Windows 8.1, Windows Server 2012 R2, and later.

AcceptEx

ConnectEx

DisconnectEx

TransmitFile

TransmitPackets

WSAEventSelect

Winsock Functions

Winsock Reference

connect

socket