服务器端程序主要是对远程客户端发出“连接”与“关闭”请求作出响应。即建立客户端与服务器端之间的连接与解除连接 客户端程序主要是向远程服务器端发出请求，提供用户下载文件和上传文件的用户界面。 -Server-side program mainly for the remote client issued a " connection" and " close" to respond to requests. Namely the establishmen