I got an error with my server program: WSAENOBUFS 10055 No buffer space available. An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full. someone said there is resource leak(sockets were not closed because of some reason). but if the leak exists, how did it occour? i close socket in the following situations: 1. WSASend() != 0 && WSAGetLastError() != WSA_IO_PENDING 2. WSARecv() != 0 && WSAGetLastError() != WSA_IO_PENDING 3. GetQueuedCompletionStatus() returns 0 but lpNumberOfBytesTransferred (the second parameter of this function) is 0 (means client socket is closed) 4. haven't received anything from a socket for 3 minutes. 5. Accept failed. is there anything i missed?

How much are you writing to your socket? Is the buffer, for that socket, actually full, because the other end isn't reading?

Have you run with Purify? Is there a heap corruption bug that prevents more allocations from happening?