服务器，使用ServerSocket监听指定的端口，端口可以随意指定（由于1024以下的端口通常属于保留端口，在一些操作系统中不可以随意使用，所以建议使用大于1024的端口），等待客户连接请求，客户连接后，会话产生；在完成会话后，关闭连接-Server, using the specified port ServerSocket listening, you can optionally specify the port (usually port as 1024 the following ports are reserved, in some operating systems can not be free to use, it is proposed to use ports greater than 1024), waiting for client connection requests, the customer connection, the session produced　in the completion of the session, close connection