说明：  本文简要的概括了目前正在流行的P2P技术及其实际运用, 防火墙的基本概念及工作方式, 以及P2P技术穿透防火墙的几种简单实现, 并且利用一个简单的C++程序, 来阐述如何通过穿透防火墙, 以实现点对点的对等连接
(This paper briefly summarizes the currently popular P2P technology and its practical application, the firewall' s basic concepts and working methods, as well as several P2P technology to penetrate the firewall is simple to implement, and use a simple C++ program to illustrate how to penetrate firewall to achieve peer-to-peer connection)