Abstract: A system and method for establishing a direct peer to peer communication link between computers connected to the Internet through symnat routers. One client computer (Client B) is instructed by a server to open a number of targets by sending packets to a range of port numbers beginning with another computer's (Client A) last known public port number. Client A is then instructed by the server to send a number of packets at the last known port used by client B but each time increasing its (Client A's) port number. If a packet is sent where the To and From ports of both client computers match, a peer to peer communication link can be established.

Abstract: A registration server and client software is configured to establish communications between first and second computers, wherein at least one of the first and second computers resides behind a symmetric network address translator.