A peer-to-peer server sends a first internal internet protocol (IP) address and a first internal port number of a first node to a second node, and sends a second internal IP address and a second internal port number of the second node to the first node. The first node sends a first packet to the second internal IP address and the second internal port number via a network address translator. The network address translator send a second packet corresponding to the first packet from an intermediary IP address and an intermediary port number to the second node. The second node sends a third packet to the intermediary IP address and the intermediary port number. The network address translator performs a lookup operation to send a fourth packet corresponding to the third packet to the first internal IP address and the first internal port number.