[Vala] I need to print Gdk.NativeWindow as an actual value, how do I print it?

[Arkadi Viner <arkashkin gmail com>]

  private static Gtk.Socket sock;
   sock = new Gtk.Socket();
    sock.show();
    this.scrolled_window.add_with_viewport(sock);
    stdout.printf("Socket ID=%ld \n", (long)sock.get_id());

it prints - "Socket ID=0"

some how in Python, this line prints an actual number on a screen:

print "Socket ID=", socket.get_id()


How do I properly do it?

Thanks in advance.