A novel IP over UDP tunneling based firewall traversal for peer-to-peer networks

The connection failure caused by firewalls has become a serious problem in P2P applications such as P2P based online game, instant message and file sharing. To address this problem, we propose a firewall traversal method using IP over UDP tunneling, and show some details of its implementation. In such a method, two peers behind firewalls create a bi-directional UDP tunnel with the help of a FTP server which has a public IP address. After that, they encapsulate IP tunnel packets (IPTP) by adding new IP and UDP headers into an IP packet, and transfer IPTP through the opened UDP tunnel. With this firewall traversal method, any peer can communicate with other peers freely and directly.