Introduction - If you have any usage issues, please Google them yourself
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.