title: How to get external port from stun server
body: <p>How to get external ip and port from stun server? For example Google's stun server, <code>stun.l.google.com</code></p>
  <p>So I can use that to establish P2P connection with sockets between clients behind NAT.</p>
  <p>Currently, I can only connect to peers in local network, but I want to connect peers outside of local network with sockets.</p>