Persistent notes

There are two normal scenarios for both WSASend() and
WSARecv() functions:

• when the function returns 0, it means that I/O operation was completed
  immediately
• when the function return SOCKET_ERROR value and WSAGetLastError() returns
  WSA_IO_PENDING, that means I/O operation was scheduled successfully and it
  will be completed later.

In other words it means, that even when you plan to manage socket I/O
operations asynchronously, you still need to handle the case, that some
operations can be competed synchronously.

If you use I/O Completion Port, there is an easy trick so that immediately
completed operations can be reported as they are completed naturally in
asynchronous order.

	iResult = WSARecv(CustomOverlapped.some_socket,
			&CustomOverlapped.wsaBuffer, 1,
			&CustomOverlapped.dwBytes,
			&CustomOverlapped.dwFlags,
			&CustomOverlapped.overlapped, NULL);

	if (((SOCKET_ERROR == iResult) && (WSA_IO_PENDING != WSAGetLastError())){
		//something went wrong
		//handle the error here
	}

	//test if operation is already completed
	if (0==iResult){
		//submit I/O completion packet to IOCP
		PostQueuedCompletionStatus(hIOCP, sizeof(CustomOverlapped), 0, &CustomOverlapped.overlapped);
	}

This will allow to postpone the handling of the operation results and also
to keep things logically clear in the source code.