Question

I am trying to have 2 way communication running between C sockets. For having the sockets set up, I was following the instructions on this link (http://www.linuxhowtos.org/C_C++/socket.htm) and everything worked fine. Sending messages from the client to the server worked perfectly.

However, I would also like the ability of the server to send response messages back to the client. How is this accomplished? If I set up a client and server connection at both ends, one of them cannot bind.

edit more code. Currently, I’ve used this style of sockets and put them into c++ code, just because that’s my familiarity. Ignore the object oriented-ness.

//main call
if (server)
    {
        Connection recv(true, "servername");
        recv.GetMsg();
        recv.SendMsg("test", 4);
    }
    else // client
    {
        Connection snd(false, "servername");
        snd.GetMsg();
        snd.SendMsg("this is a test", 14);
    }

And inside the Connection class,

void SendMsg(char *msg, int msg_length)
{
        send(some_socket, msg, msg_length, 0);
};

void GetMsg()
{
        recvd = recv(opponent_socket, buffer, sizeof(buffer), 0);
        buffer[recvd] = '\0';
        cout << "Printing msg: " << buffer << endl;
};

Connection::Connection(bool isserver, char *servername)
{
    is_server = isserver;
    server = servername;
    opponent_socket = 0;
    some_socket = socket(PF_INET, SOCK_STREAM, 0);

    if (some_socket < 0)
    {
        cout << "Connection failed.\n" << endl;
        exit(-1);
    }

    if (is_server)
    {
        AddrSetupServer(); // standard calls here.  Pretty well what's shown in link provided
        BindServer();
        ListenServer();
        WaitConnectionServer();
    }
    else
    {
        AddrSetupClient();
        ConnectClient();
    }
};

Answer 1

Once you have a connection, it is bidirectional; simply send your response over the socket.