how to send local IP address of a server?

[beginner123]

i have created a client and server app in c++ using TCP. The server needs to send its ip address to a web host. The web host is a php script that adds and removes the ip addresses of the servers. The client app then connects to this web host, receives the list of addresses and then displays them in a listbox. The server did send the external ip fine but now i want it to send the local ip but its sending 0.0.0.0 instead of the local address

on line 143 i tried sending the local address

here is all of the server code:

#define WEBSITE         "server.x10host.com"    // Full website URL, withouth HTTP (raises exe size)
    #define WEBPAGE         "/Server.php"               // The page of the Server Script (proceed with '\')


    #define cAddIP          0       // Send this to the server, to add the IP to the list.
    #define cRemIP          1       // Send this to the server, to remove the IP from the list.
    #define cGetIPs         2       // Send this to the server, to get the list of all IPs.


SOCKET ListeningSocket;
SOCKADDR_IN ServerAddr;

int Port = 7171;
char* MyIP;                     // Hold's the computers external IP (EG on an NAT)

// -------------------------




char* WebPost(char Website[], char Webpage[], char Request[], int RetLen) {
    // Sends an HTTP Post request with POST Data...
    // Absolutly NOT error checking, which needs fixing!

    SOCKET WebSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    struct hostent *WebHost;
    WebHost = gethostbyname(Website);
    if (WebHost == NULL) {

        if (WSAGetLastError() == WSANOTINITIALISED)
            printf("Error Not Connected!");
        else
            printf("Error: %d", WSAGetLastError());

        Sleep(1000);
        exit(0);

    }
    SOCKADDR_IN SockAddr;
    SockAddr.sin_port   = htons(80);
    SockAddr.sin_family = AF_INET;

    SockAddr.sin_addr.s_addr = *((unsigned long*)WebHost->h_addr);
    connect(WebSocket, (SOCKADDR*)(&SockAddr), sizeof(SockAddr));


    char PostRequest[1024];

    sprintf(PostRequest,
        "POST %s HTTP/1.1\r\n"
        "Host: %s\r\n"
        "Content-Length: %hu\r\n"
        "Content-Type: application/x-www-form-urlencoded\r\n"
        "\r\nD=%s\0",
        Webpage, Website,
        strlen(Request)+2, Request
    );

    send(WebSocket, PostRequest, strlen(PostRequest), 0);


    // Get return data ----------

    char* Data = new char[RetLen];
    recv(WebSocket, Data, 4, 0);

    for (;;) {                          // Skip HTTP headers...

        Data[0] = Data[1];
        Data[1] = Data[2];
        Data[2] = Data[3];

        recv(WebSocket, &Data[3], 1, 0);

        if (Data[0] == '\r' && Data[1] == '\n'
        &&  Data[2] == '\r' && Data[3] == '\n')
            break;

    }

    int DataLen = recv(WebSocket, Data, RetLen, 0);
    Data[DataLen] = '\0';   // Return the data...

    shutdown(WebSocket, 2);
    closesocket(WebSocket);
    return Data;

}



void ServStart() {

    WSADATA wsaData; 

    if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0) {
        printf("Server: WSAStartup failed with error %ld.\n", WSAGetLastError());
        exit(0);
    }

    printf("Server: The Winsock DLL found!\n");
    printf("Server: The current status is %s.\n\n", wsaData.szSystemStatus);

    if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2 ) {
        printf("Server: The dll do not support the Winsock version %u.%u!\n", LOBYTE(wsaData.wVersion),HIBYTE(wsaData.wVersion));
        WSACleanup();
        exit(0);
    }

    printf("Server: The dll supports the Winsock version %u.%u!\n", LOBYTE(wsaData.wVersion),HIBYTE(wsaData.wVersion));


    // Start listening -----------------------------------------------
    ListeningSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    if (ListeningSocket == INVALID_SOCKET) {
        printf("Server: Error at socket, error code: %ld.\n", WSAGetLastError());
        WSACleanup();
        exit(0);
    }

    ServerAddr.sin_family = AF_INET;
    ServerAddr.sin_port = htons(Port);
    ServerAddr.sin_addr.s_addr = htonl(INADDR_ANY);

    if (bind(ListeningSocket, (SOCKADDR *)&ServerAddr, sizeof(ServerAddr)) == SOCKET_ERROR) {
        printf("Server: bind failed! Error code: %ld.\n", WSAGetLastError());
        closesocket(ListeningSocket);
        WSACleanup();
        exit(0);
    }

    if (listen(ListeningSocket, 5) == SOCKET_ERROR) {
        printf("Server: listen: Error listening on socket %ld.\n", WSAGetLastError());
        closesocket(ListeningSocket);
        WSACleanup();
        exit(0);
    }


    //MyIP = WebPost("api.externalip.net", "/ip/", "", 16);   // Get my IP
    MyIP = inet_ntoa(ServerAddr.sin_addr);
    char SendBuf[32];
    sprintf(SendBuf, "%hhu|%s", cAddIP, MyIP);      // Send the server the IP
    WebPost(WEBSITE, WEBPAGE, SendBuf, 0);

    printf("Server: listening for connections...\n\n");

}

void ShutDown() {               // Shut down the server (tells the web server I am offline)

    char SendBuf[32];           // Remove my IP from the list of online servers...
    sprintf(SendBuf, "%hhu|%s", cRemIP, MyIP);
    WebPost(WEBSITE, WEBPAGE, SendBuf, 0);

    printf("Successful shutdown\n");
    Sleep(1000);

    WSACleanup();

}

//


void ServLoop() {

    SOCKADDR_IN SenderInfo;
    SOCKET NewConnection;

    int ByteReceived, nlen;
    char recvbuff[1024];

    for (;;) {                                                      // Main program loop

        NewConnection = SOCKET_ERROR;
        while(NewConnection == SOCKET_ERROR) {

            NewConnection = accept(ListeningSocket, NULL, NULL);    // (this is a blocking function)
            printf("Server: New client got connected, ready to receive and send data...\n\n");

            ByteReceived = recv(NewConnection, recvbuff, sizeof(recvbuff), 0);

            if (ByteReceived > 0) {

                getsockname(ListeningSocket, (SOCKADDR *)&ServerAddr, (int *)sizeof(ServerAddr));
                printf("Server: IP(s) used by Server: %s\n", inet_ntoa(ServerAddr.sin_addr));
                printf("Server: port used by Server: %d\n\n", htons(ServerAddr.sin_port));

                memset(&SenderInfo, 0, sizeof(SenderInfo));
                nlen = sizeof(SenderInfo);

                getpeername(NewConnection, (SOCKADDR *)&SenderInfo, &nlen);

                printf("Server: IP used by Client: %s\n", inet_ntoa(SenderInfo.sin_addr));
                printf("Server: Port used by Client: %d\n", htons(SenderInfo.sin_port));

                printf("Server: Bytes received: %d\n", ByteReceived);
                printf("Server: Those bytes are: \n\"");

                for(int i = 0; i < ByteReceived; ++i)
                    printf("%c", recvbuff[i]);

                printf("\"");

            } else if ( ByteReceived == 0 )
                printf("Server: Connection closed!\n");
            else
                printf("Server: recv failed with error code: %d\n", WSAGetLastError());

        }

        if (shutdown(NewConnection, 2) != 0)
            printf("\n\nServer: there is something wrong with the shutdown. The error code: %ld\n", WSAGetLastError());
        else
            printf("\nServer: shutdown is working...\n");

    }

}


// --------------------------------------------




BOOL ConsoleProc(DWORD Msg) {

    switch (Msg) {

        case CTRL_CLOSE_EVENT:
        case CTRL_LOGOFF_EVENT:
        case CTRL_SHUTDOWN_EVENT:
            ShutDown();
        return false;

    }

    return false;

} 

int main(/*int argc, char **argv*/) {

    // Handle console events
    SetConsoleCtrlHandler((PHANDLER_ROUTINE)ConsoleProc, TRUE);

    ServStart();            // Main loop is in another thread
    ServLoop();             // The never returning server loop

}

[modoran]

I really don't see the point of using http://api.externalip.net/ip/ , as the PHP script will get your external IP address anyway using $_SERVER['REMOTE_ADDR'];

As for your question, On windows, don't use WinSock at all to get the local IPs. Use GetAdaptersInfo() and/or GetAdapterAddresses() instead.

[coder777]

use gethostname(). See example:

http://stackoverflow.com/questions/122208/get-the-ip-address-of-local-computer

[beginner123]

ok so i changed line 143 to char MyIP = gethostbyname(SendBuf);
but i get this error: error C2440: '=' : cannot convert from 'hostent *' to 'char *'

[beginner123]

@modoran what code do i need to add for GetAdaptersInfo() or GetAdapterAddresses()?

[coder777]

well, look at line 28. It shows the use of gethostbyname().

Do not SendBuf as the parameter (even if it's the next thing available). Use gethostname(). Take a look at the example provided:

http://tangentsoft.net/wskfaq/examples/ipaddr.html

[beginner123]

ok so what should i send as the parameter?
and i need to create a another struct like the example you linked?
struct hostent *phe = gethostbyname(ac);

[beginner123]

also by sending the host name how does that send the ip address?
i want to send the ip address of the computer to the web host so i think using GetAdaptersAddresses() will be better

can someone please post some code on how to use the GetAdaptersAddresses() function?

[coder777]

from GetAdaptersAddresses() you don't get other information than gethostbyname():

    char ac[80];
    if (gethostname(ac, sizeof(ac)) == SOCKET_ERROR) {
        cerr << "Error " << WSAGetLastError() <<
                " when getting local host name." << endl;
        return 1;
    }
    cout << "Host name is " << ac << "." << endl;

    struct hostent *phe = gethostbyname(ac);
    if (phe == 0) {
        cerr << "Yow! Bad host lookup." << endl;
        return 1;
    }

        struct in_addr addr;
        memcpy(&addr, phe->h_addr_list[0], sizeof(struct in_addr)); // use the first ip-address
        cout << "Address " << i << ": " << inet_ntoa(addr) << endl; // inet_ntoa(addr) provides the address you want. 

[beginner123]

so if inet_ntoa(addr) provides the address why won't it work when i try sending it to the web host?

[coder777]

There're serveral reasons: firewall, router

did you check if inet_ntoa(addr) returns a valid ip?

no matter whether you use GetAdaptersAddresses() or gethostbyname() you get indeed the local ip, which is accessible in the local network only, not the internet

[beginner123]

the code you gave worked and i set MyIP = inet_ntoa(addr);