说明：  一个模拟p2p聊天的过程的源代码，过程很简单，p2pserver运行在一个拥有公网ip的计算机上，p2pclient运行在两个不同的nat后（注意，如果两个客户端运行在一个nat后，本程序很可能不能运行正常，这取决于你的nat是否支持loopback translation，详见http://midcom-p2p.sourceforge.net/draft-ford-midcom-p2p-01.txt，当然，此问题可以通过双方先尝试连接对方的内网ip来解决，但是这个代码只是为了验证原理，并没有处理这些问题），后登录的计算机可以获得先登录计算机的用户名，后登录的计算机通过send username message的格式来发送消息。如果发送成功，说明你已取得了直接与对方连接的成功
(A process simulation p2p chat source code, the process is very simple, p2pserver running on a LAN with a public ip on the computer, p2pclient run on two different nat after (Note that if two clients running on a nat, the program is likely not run properly, depending on whether your nat support loopback translation, see http://midcom-p2p.sourceforge.net/draft-ford-midcom-p2p-01.txt, of course, this problem can be the two sides first try to connect to each other s network ip resolved, but this code is just to verify the principle, and did not deal with these issues), after the logon computer can get logged in the computer s user name, computer and log in through the send username message format to send a message. If the transmission was successful, that you have made to connect directly with each other s success.)