public class EchoServer extends ChannelInboundHandlerAdapter {
    /**
     * 读取事件
     * @param ctx
     * @param msg
     * @throws Exception
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf in = (ByteBuf) msg;
        System.err.println("Server receive" + in.toString(CharsetUtil.UTF_8));
    }
    /**
     * 最后一次读取完成之后，发送通知到channelHandler
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
    }
    /**
     * 读取的过程
     * @param ctx
     * @param cause
     * @throws Exception
     */
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}
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public class EchoServerClient {
    private static final int PORT = 8080;
    public static void main(String[] args) throws InterruptedException {
        if(args.length > 1){
            System.err.println("server ");
        }
        final EchoServer echoServer = new EchoServer();
        // 创建事件驱动器 EventLoopGroup
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try{
            // 创建server bootstrap
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            // 1. 指定使用NIO传输的渠道
            // 2. 指定端口
            // 3. 添加一个echoseverhandler 到子channel的chanelPipeline
            serverBootstrap.group(eventLoopGroup)
                    .channel(NioServerSocketChannel.class)
                    .localAddress(new InetSocketAddress(PORT))
                    .childHandler(new ChannelInitializer() {
                        // 很关键，需要使用pipeline加入事件来帮我们处理channel
                        protected void initChannel(Channel ch) throws Exception {
                            ch.pipeline().addLast(echoServer);
                        }
                    });
            // 阻塞当前线程，异步绑定服务器
            ChannelFuture channelFuture = serverBootstrap.bind().sync();
            // 获取当前channel的closeFuture，阻塞直到线程完成
            channelFuture.channel().closeFuture().sync();
        }finally {
            // 关闭group 释放资源
            eventLoopGroup.shutdownGracefully().sync();
        }
    }
}
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