说明：  面向连接的Socket实例: 代码实例中的服务器通过socket连接向客户端发送字符串"Hello, you are connected!"。只要在服务 器上运行该服务器软件，在客户端运行客户软件，客户端就会收到该字符串。
(Connection-oriented Socket example: code of server instances to connect through the socket to the client to send the string " Hello, you are connected!" . As long as the server running the server software, running on the client client, the client will receive the string.)