Question

I am following a tutorial that teaches me how to use win32 sockets(winsock2). I am attempting to create a simple socket that connects to the “localhost” but my program is failing when I attempt to connect to the local host(at the function connect()).

Do I need admin privileges to connect to the localhost? Maybe thats why it fails? Maybe theres a problem with my code? I have tried the ports 8888 & 8000 & they both fail.

Also if I change the port to 80 & connect to http://www.google.com I can connect BUT I get no response back. Is that because I haven’t sent a HTTP request or am I meant to get some response back?

Here’s my code (with the includes removed):

// Constants & Globals //
typedef unsigned long IPNumber;    // IP number typedef for IPv4
const int SOCK_VER    = 2;
const int SERVER_PORT = 8888;  // 8888
SOCKET mSocket        = INVALID_SOCKET;
SOCKADDR_IN sockAddr  = {0};
WSADATA wsaData;
HOSTENT* hostent;


int _tmain(int argc, _TCHAR* argv[])
{
    // Initialise winsock version 2.2
    if (WSAStartup(MAKEWORD(SOCK_VER,2), &wsaData) != 0)
    {
        printf("Failed to initialise winsock\n");
        WSACleanup();
        system("PAUSE");
        return 0;
    }

    if (LOBYTE(wsaData.wVersion) != SOCK_VER || HIBYTE(wsaData.wVersion) != 2)
    {
        printf("Failed to load the correct winsock version\n");
        WSACleanup();
        system("PAUSE");
        return 0;
    }

    // Create socket
    mSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (mSocket == INVALID_SOCKET)
    {
        printf("Failed to create TCP socket\n");
        WSACleanup();
        system("PAUSE");
        return 0;
    }


    // Get IP Address of website by the domain name, we do this by contacting(??) the Domain Name Server
    if ((hostent = gethostbyname("localhost")) == NULL)  // "localhost"  www.google.com
    {
        printf("Failed to resolve website name to an ip address\n");
        WSACleanup();
        system("PAUSE");
        return 0;
    }

    sockAddr.sin_port             = htons(SERVER_PORT);
    sockAddr.sin_family           = AF_INET;
    sockAddr.sin_addr.S_un.S_addr = (*reinterpret_cast <IPNumber*> (hostent->h_addr_list[0]));
    // sockAddr.sin_addr.s_addr=*((unsigned long*)hostent->h_addr);  // Can also do this

    // ERROR OCCURS ON NEXT LINE: Connect to server
    if (connect(mSocket, (SOCKADDR*)(&sockAddr), sizeof(sockAddr)) != 0)
    {
        printf("Failed to connect to server\n");
        WSACleanup();
        system("PAUSE");
        return 0;
    }

    printf("Got to here\r\n");
    // Display message from server
    char buffer[1000];
    memset(buffer,0,999);
    int inDataLength=recv(mSocket,buffer,1000,0);
    printf("Response: %s\r\n", buffer);

    // Shutdown our socket
    shutdown(mSocket, SD_SEND);

    // Close our socket entirely
    closesocket(mSocket);

    // Cleanup Winsock
    WSACleanup();

    system("pause");
    return 0;
}

Answer 1

Someone should be listening in the port you are connecting to. Try writing a small server program that will listen for incoming connections. If connect succeeds obviously you are connected to google but you need to send a HTTP request (from C? – that would be difficult).