说明：  网络通信编程，socket编程，socket服务器端程序，可运行。代码简单完整，注释清晰，linux下编译通过，可运行。适合socket编程入门参考。
(Network Communication Programming, socket program, socket server-side program can be run. Simple complete code, comments clear, linux under the compiler is passed, can be run. Reference entry for socket programming.)