1) 利用InetAddress类的方法获取主机的名称和IP地址。

2) 利用URL类获取网络资源。

3) 使用Socket编程：客户机发送数据到服务器，服务器将接收到的数据返回给客户机，运用多线程机制，实现服务器同时处理多个客户机的请求。

4) 使用UDP编程：客户机发送数据到服务器，服务器将接收到的数据返回给客户机， 实现一个模拟电子邮件的发送和接收的UDP程序。

-1) using InetAddress class method to get the host name and IP address. 2) the use of URL-type access network resources. 3) the use of Socket Programming: client sends data to the server, the server will receive the data back to the client, using multi-thread mechanism, the realization of the server to handle multiple client requests. 4) the use of UDP programming: client sends data to the server, the server will receive the data back to the client to achieve a simulated e-mail sending and receiving the UDP process.