TCPBridge: A Software Approach to Establish Direct Communications for NAT Hosts

Traversing Network Address Translation (NAT) for Peer-To-Peer (P2P) communication has become a hot topic recently. Compared to UDP, establishing TCP connections for hosts behind different NATs is more complex. Thus, many TCP-based applications do not address TCP traversal through NATs. Some solutions suggest using delegates to relay all communications, or tunneling TCP over UDP. However, they require a big reform to network architecture, or using a nonstandard TCP/IP stack. In this paper, the authors present a novel idea called TCPBridge. TCPBridge converts TCP traversal to UDP traversal without modifying any binaries of the TCP-based applications.