说明：  数据通讯与网络教程是进行网络编程和数据通信人员的一本圣经，共分为十部分，这是第四部分，尤其对准备从事网络编程、数据通信编程的工程人员具有指导意义。
(data communication and network Guide is network programming and data communications staff of a Bible, is divided into 10 parts, This is the fourth part, in particular the right to engage in network programming, data communications programming staff is instructive.)