Hi, src\aio\usock_win.inc, line: 454wflags = MSG_WAITALL; wsarecv is not supported MSG_WAITALL with TCP socket, MSDN says:"Be aware that if the underlying transport provider does not supportMSG_WAITALL, or if the socket is in a non-blocking mode, then this call will fail with WSAEOPNOTSUPP" With:wflags = MSG_WAITLL; wsarecv wont block, and return immediatly. How block wsarecv with Windows XP? best regards, Ranier Vilela