客户端程序。该程序首先与相应服务器连接。然后接收用户从标准输入（键盘）输入的字符串，再将字符串发送给服务器，接收服务器发回的信息并显示。之后，继续等待用户输入直至用户输入Ctrl-D。当收到用户输入Ctrl-D后，客户关闭连接并退出。-client. The procedure first with the corresponding server connections. Users then receive from the standard input (keyboard) and input string, and then a string sent to the server, server to receive the information and display. After continue to wait until the user input of user input Ctrl-D. When users type Ctrl-D, customers close the connection and exit.