说明：  linux下使用socket进行网络通信，含server.c和client.c文件，使用时可以将server.c在PC linux下运行，client.c经交叉编译后下到开发板运行
(linux network using socket communications, including server.c and client.c documents, can be used server.c in the PC linux run, client.c by cross-compiled to run under the development board)