praschat 0 Newbie Poster

I want to know how to connect two computers directly in NAT environment. In this connection, I found out a solution called UDP hole punching., where at first a rendezvous server is required to be connected by both the computers to send their IP and port address which is exchanged between two computers and thereafter they can send messages to each other directly.

My point is how to get the Visitor's port address? which is assigned by their ISPs NAT program.