#include <winsock2.h> #include <stdio.h> .... int in; ... if (WSAIoctl(sn, SIO_RCVALL, &j, sizeof(j), 0, 0, &in, 0, 0) == SOCKET_ERROR) { MessageBox (HWND_DESKTOP, "WSAIoctl() failed.", "Error", MB_OK | MB_ICONEXCLAMATION); return 1; } ......