NAT穿越的java网络编程，一个服务器端，两个客户端，代码详细，测试通过了

这个代码实现了UDP协议的NAT穿越，简单设计课客户端和服务器端，已经试验过，能够出现打洞过程。(This code has been implemented NAT traversing of UDP protocol.Simple design course of client and server, which has been tested, can make hole.)