WSAGetOverlappedResult

The Windows Sockets WSAGetOverlappedResult function returns the results of an overlapped operation on the specified socket.

BOOL WSAGetOverlappedResult (
  SOCKET s,                      
  LPWSAOVERLAPPED lpOverlapped,  
  LPDWORD lpcbTransfer,          
  BOOL fWait,                    
  LPDWORD lpdwFlags              
);

Parameters

s: [in] A descriptor identifying the socket. This is the same socket that was specified when the overlapped operation was started by a call to WSARecv, WSARecvFrom, WSASend, WSASendTo, or WSAIoctl.
lpOverlapped: [in] A pointer to a WSAOVERLAPPED structure that was specified when the overlapped operation was started.
pcbTransfer: [out] A pointer to a 32-bit variable that receives the number of bytes that were actually transferred by a send or receive operation, or by WSAIoctl.
fWait: [in] A flag that specifies whether the function should wait for the pending overlapped operation to complete. If TRUE, the function does not return until the operation has been completed. If FALSE and the operation is still pending, the function returns FALSE and the WSAGetLastError function returns WSA_IO_INCOMPLETE. The fWait parameter may be set to TRUE only if the overlapped operation selected the event-based completion notification.
lpdwFlags: [out] A pointer to a 32-bit variable that will receive one or more flags that supplement the completion status. If the overlapped operation was initiated through WSARecv or WSARecvFrom, this parameter will contain the results value for lpFlags parameter.

Remarks

The WSAGetOverlappedResult function reports results of last overlapped operation for the specified socket. The WSAOverlappedResult function is passed the socket descriptor and the WSAOVERLAPPED structure that were specified when the overlapped function was called. A pending operation is indicated when the function that started the operation returns FALSE and the WSAGetLastError function returns WSA_IO_PENDING. When an I/O operation such as WSARecv is pending, the function that started the operation resets the hEvent member of the WSAOVERLAPPED structure to the nonsignaled state. Then when the pending operation has completed, the system sets the event object to the signaled state.

If the fWait parameter is TRUE, WSAGetOverlappedResult determines whether the pending operation has been completed by waiting for the event object to be in the signaled state.A client may set fWait parameter to TRUE only if it selected event-based completion notification when the IO operation was requested. If another form of notification was selected, the usage of the hEvent parameter of the WSAOVERLAPPED structure is different, and setting fWait to TRUE causes unpredictable results.

Return Values

If WSAGetOverlappedResult succeeds, the return value is TRUE. This means that the overlapped operation has completed successfully and that the value pointed to by lpcbTransfer has been updated. If WSAGetOverlappedResult returns FALSE, this means that either the overlapped operation has not completed, the overlapped operation completed but with errors, or the overlapped operation's completion status could not be determined due to errors in one or more parameters to WSAGetOverlappedResult. On failure, the value pointed to by lpcbTransfer will not be updated. Use WSAGetLastError to determine the cause of the failure (either of WSAGetOverlappedResult or of the associated overlapped operation).

Error Codes

WSANOTINITIALISED	A successful WSAStartup must occur before using this function.
WSAENETDOWN	The network subsystem has failed.
WSAENOTSOCK	The descriptor is not a socket.
WSA_INVALID_HANDLE	The hEvent field of the WSAOVERLAPPED structure does not contain a valid event object handle.
WSA_INVALID_PARAMETER	One of the parameters is unacceptable.
WSA_IO_INCOMPLETE	The fWait parameter is FALSE and the I/O operation has not yet completed.
WSAEFAULT	One or more of the lpOverlapped, lpcbTransfer, or lpdwFlags arguments are not a valid part of the user address space.

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