WSACleanup

The Windows Sockets WSACleanup function terminates use of the Windows Sockets DLL.

int WSACleanup (void);

Remarks

An application or DLL is required to perform a successful WSAStartup call before it can use Windows Sockets services. When it has completed the use of Windows Sockets, the application or DLL must call WSACleanup to deregister itself from a Windows Sockets implementation and allow the implementation to free any resources allocated on behalf of the application or DLL. Any pending blocking or asynchronous calls issued by any thread in this process are canceled without posting any notification messages, or signaling any event objects. Any pending overlapped send and receive operations (WSASend/WSASendTo/WSARecv/WSARecvFrom with an overlapped socket) issued by any thread in this process are also canceled without setting the event object or invoking the completion routine, if specified. In this case, the pending overlapped operations fail with the error status WSA_OPERATION_ABORTED. Any sockets open when WSACleanup is called are reset and automatically deallocated as if closesocket was called; sockets which have been closed with closesocket but which still have pending data to be sent may be affectedthe pending data may be lost if the Windows Sockets DLL is unloaded from memory as the application exits. To insure that all pending data is sent an application should use shutdown to close the connection, then wait until the close completes before calling closesocket and WSACleanup. All resources and internal state, such as queued un-posted messages, must be deallocated so as to be available to the next user.

There must be a call to WSACleanup for every successful call to WSAStartup made by a task. Only the final WSACleanup for that task does the actual cleanup; the preceding calls simply decrement an internal reference count in the Windows Sockets DLL.

Return Values

The return value is zero if the operation was successful. Otherwise, the value SOCKET_ERROR is returned, and a specific error number may be retrieved by calling WSAGetLastError.

Comments

Attempting to call WSACleanup from within a blocking hook and then failing to check the return code is a common Windows Sockets programming error. If an application needs to quit while a blocking call is outstanding, the application must first cancel the blocking call with WSACancelBlockingCall then issue the WSACleanup call once control has been returned to the application.

In a multithreaded environment, WSACleanup terminates Windows Sockets operations for all threads.

Error Codes

WSANOTINITIALISED	A successful WSAStartup must occur before using this function.
WSAENETDOWN	The network subsystem has failed.
WSAEINPROGRESS	A blocking Windows Sockets 1.1 call is in progress, or the service provider is still processing a callback function.

See Also

closesocket, shutdown, WSAStartup

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