本程序是结合非阻塞模式通道类、选择器和缓冲区等对象实现服务器和客户端的通信。在服务器端监听客户端的连接，服务器接收客户端发送的消息，并将这些消息转换为大写文本返回客户端，并在服务器端显示。-This procedure is a combination of non-blocking mode channel type, the selector and buffer to achieve such objects server and client communications. Monitor the client on the server side connection, the server receives the message sent by the client, and these messages are converted to uppercase text returned to the client and the server side display.