select() not picking up stdin

Question

I have this:

    #define STDIN 0 

    char buffer[512];
    bzero(buffer,512);
    struct sockaddr_in from;
    string input;
    RoutingMessage parser;

    cout << "Listening...\n";

        /* Temporary fix. 
    /* This should be abstracted, and more widely used
    /********* Start Select() ***********/
    fd_set readfds;
    struct timeval tv;
    tv.tv_sec = 120;
    tv.tv_usec = 0; //wait for 1.5 second here

    int rv = 1;

    // clear the set ahead of time
    FD_ZERO(&readfds);

    // add our descriptors to the set
    FD_SET(mySocket, &readfds);
    FD_SET(STDIN, &readfds);

    // the n param for select()
    int n = mySocket + 1;
    /********* End Select() ***********/

    while(rv != 0)
    {
        rv = select(n, &readfds, NULL, NULL, &tv);

        if (rv == -1)
            perror("select"); // error occurred in select()

        if (FD_ISSET(STDIN, &readfds))
        {
                cin >> input;
                cout << input << endl;
        }
        else
        {
            bzero(buffer,512);
            int n = recvfrom(mySocket,buffer,512,0,(struct sockaddr *)&from, &sockLen);

            if (n < 0) 
                perror("recvfrom");

            if (n > 0)
            {
                parser.ParseMessage(buffer, fromNode, messages);
                ProcessMessages();
            }
         }
    }

However, when I try to type anything in my program, I don't get the response from cout:

Listening...
3702 has converged!
3701 has converged!
3703 has converged!
test
// blank line

Am I doing something wrong?

Answer 1

select alters the readfds you pass in to it. You'll have to provide the file descriptors you want to watch for events each time you call select. e.g.

while(rv != 0) {
  FD_ZERO(&readfds);
  FD_SET(mySocket, &readfds);
  FD_SET(STDIN, &readfds);
  rv = select(n, &readfds, NULL, NULL, &tv);