> I can't see how the post you linked actually does the NAT traversal... It assumes full-cone NAT - you punch a hole once by sending a packet to a third party,

> I can't see how the post you linked actually does the NAT traversal... It assumes full-cone NAT - you punch a hole once by sending a packet to a third party, like a stun server which will along the way tell you your external ip:port, and then a full-cone NAT would forward packets coming to that ip:port back to you, regardless of the source.