The Research On NAT Traversal Of TCP Based On Incomplete Third-party Agent Server

NAT traversal is a technology that establish a connection between a host which in a private TCP/IP network of using NAT equipment, it’s wide application and pay close attention to the industry. UDP-based NAT Traversal technology has been basically mature, so research focused on the TCP-based. The more commonly used TCP traversal NAT technology is based on the third-party agent server, two client completed NAT traversal under the assistance of a third-party agent server.This paper will explore a kind of technology to replace the current TCP Traversal NAT technology based on the third-party agent server--Using IMAP and SMTP instead of third-party agent server. We will achieve the public network IP address from ip138website and complete communication between peers with E-Mail, using the feature of TCP protocol to realize port prediction, and processing TCP packets with WinPcap.By our experiment, we show that a scheme without the third-party agent server and with commonly internet services is feasible.