穿越NAT建立TCP连接

TCP Connectivity Through Network Address Translators

网络地址转换(Network Address Translation,NAT)技术已经被广泛应用,得到了多数防火墙/网关设备的支持。目前穿越NAT都是基于UDP实现的。由于TCP连接的建立存在状态转换,相比UDP,穿越Restriced型NAT建立TCP连接存在更大的困难。通过分析NAT穿越的技术原理和现有方法,分情况给出一种通信双方都在NAT之后时建立TCP连接的方法。

Network Address Translation （NAT） is becoming increasingly prevalent, and supported by many firewall devices. This poses a significant problem for connection establishment for peer - to - peer applications. Now most solutions implement base on UDP. The establishing of TCP connection involves states transition. Compared to UDP, establishing TCP connection has more complexity. This paper analyzes current methods used for UDP circumstance, and proposes a mechanism to create direct TCP connections between two hosts behind NATs for different environments.