#include <winsock2.h> 
#include <ws2tcpip.h> 
#include <stdio.h> 
#include <windows.h> 
#pragma comment(lib, "wininet.lib") 
 
int __cdecl main() 
{ 
 
    //--------------------------------------------- 
    // Declare and initialize variables 
    WSADATA wsaData; 
    WSABUF DataBuf; 
 
    WSAOVERLAPPED Overlapped = { 0 }; 
    SOCKET SendToSocket = INVALID_SOCKET; 
 
    struct sockaddr_in RecvAddr; 
    struct sockaddr_in LocalAddr; 
    int RecvAddrSize = sizeof (RecvAddr); 
    int LocalAddrSize = sizeof (LocalAddr); 
 
    int Port = 27015; 
    struct hostent *localHost; 
    char *ip; 
 
    char SendBuf[1024] = "Data buffer to send"; 
    int BufLen = 1024; 
    DWORD BytesSent = 0; 
    DWORD Flags = 0; 
 
    int rc, err; 
    int retval = 0; 
 
    //--------------------------------------------- 
    // Initialize Winsock 
    // Load Winsock 
    rc = WSAStartup(MAKEWORD(2, 2), &wsaData); 
    if (rc != 0) { 
        fprintf(stderr, "Unable to load Winsock: %d\n", rc); 
        return 1; 
    } 
    // Create an event handle and setup an overlapped structure. 
    Overlapped.hEvent = WSACreateEvent(); 
    if (Overlapped.hEvent == NULL) { 
        fprintf(stderr, "WSACreateEvent failed: %d\n", WSAGetLastError()); 
        WSACleanup(); 
        return 1; 
    } 
    //--------------------------------------------- 
    // Create a socket for sending data 
    SendToSocket = 
        WSASocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP, NULL, 0, 
                  WSA_FLAG_OVERLAPPED); 
    if (SendToSocket == INVALID_SOCKET) { 
        fprintf(stderr, "socket failed: %d\n", WSAGetLastError()); 
        WSACloseEvent(Overlapped.hEvent); 
        WSACleanup(); 
        return 1; 
    } 
    //--------------------------------------------- 
    // Set up the RecvAddr structure with the IP address of 
    // the receiver (in this example case "123.123.123.1") 
    // and the specified port number. 
    RecvAddr.sin_family = AF_INET; 
    RecvAddr.sin_port = htons(Port); 
    RecvAddr.sin_addr.s_addr = inet_addr("123.123.123.1"); 
 
    //--------------------------------------------- 
    // Set up the LocalAddr structure with the local IP address 
    // and the specified port number. 
    localHost = gethostbyname(""); 
    ip = inet_ntoa(*(struct in_addr *) *localHost->h_addr_list); 
 
    LocalAddr.sin_family = AF_INET; 
    LocalAddr.sin_addr.s_addr = inet_addr(ip); 
    LocalAddr.sin_port = htons(Port); 
 
    //--------------------------------------------- 
    // Bind the sending socket to the LocalAddr structure 
    // that has the internet address family, local IP address 
    // and specified port number.   
    rc = bind(SendToSocket, (struct sockaddr *) &LocalAddr, LocalAddrSize); 
    if (rc == SOCKET_ERROR) { 
        fprintf(stderr, "bind failed: %d\n", WSAGetLastError()); 
        WSACloseEvent(Overlapped.hEvent); 
        closesocket(SendToSocket); 
        WSACleanup(); 
        return 1; 
    } 
    //--------------------------------------------- 
    // Send a datagram to the receiver 
    printf("Sending a datagram...\n"); 
    DataBuf.len = BufLen; 
    DataBuf.buf = SendBuf; 
    rc = WSASendTo(SendToSocket, &DataBuf, 1, 
                   &BytesSent, Flags, (SOCKADDR *) & RecvAddr, 
                   RecvAddrSize, &Overlapped, NULL); 
 
    if ((rc == SOCKET_ERROR) && (WSA_IO_PENDING != (err = WSAGetLastError()))) { 
        fprintf(stderr, "WSASendTo failed: %d\n", err); 
        WSACloseEvent(Overlapped.hEvent); 
        closesocket(SendToSocket); 
        WSACleanup(); 
        return 1; 
    } 
 
    rc = WSAWaitForMultipleEvents(1, &Overlapped.hEvent, TRUE, INFINITE, TRUE); 
    if (rc == WSA_WAIT_FAILED) { 
        fprintf(stderr, "WSAWaitForMultipleEvents failed: %d\n", 
                WSAGetLastError()); 
        retval = 1; 
    } 
 
    rc = WSAGetOverlappedResult(SendToSocket, &Overlapped, &BytesSent, 
                                FALSE, &Flags); 
    if (rc == FALSE) { 
        printf("WSASendTo operation failed: %d\n", WSAGetLastError()); 
        retval = 1; 
    } 
 
    //--------------------------------------------- 
    // When the application is finished sending, close the socket. 
    printf("Finished sending. Closing socket.\n"); 
    WSACloseEvent(Overlapped.hEvent); 
    closesocket(SendToSocket); 
    printf("Exiting.\n"); 
 
    //--------------------------------------------- 
    // Clean up and quit. 
    WSACleanup(); 
    return (retval); 
}