课程作业，用tcl自带的套接字命令编写的一个C/S小程序。可以实现向客户端循环发送数字，客户端把接收到的数字乘2发回服务端。每发回一个，才能接受下一个命令。-Course work, the socket comes with tcl commands written in a C/S applet. Can send digital loop to the client, the client to receive digital service by 2 back end. Each sends back an order to accept the next command.