服务端

EchoServer

public class EchoServer  {
    private final int port;
    public EchoServer(int port) {
        this.port = port;
    }
    public static void main(String[] args) throws InterruptedException {
        int port = 9999;
        EchoServer echoServer = new EchoServer(port);
        System.out.println("服务器即将启动");
        echoServer.start();
        System.out.println("服务器关闭");
    }
    public void start() throws InterruptedException {
        final EchoServerHandler serverHandler = new EchoServerHandler();
        // 线程组
        EventLoopGroup group  = new NioEventLoopGroup();
        try {
            //服务端启动必备
            ServerBootstrap b = new ServerBootstrap();
            b.group(group)
             //指定使用NIO的通信模式
            .channel(NioServerSocketChannel.class)
             //指定监听端口
            .localAddress(new InetSocketAddress(port))
            .childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                protected void initChannel(SocketChannel ch) throws Exception {
                    ch.pipeline().addLast(serverHandler);
                }
            });
            //异步绑定到服务器，sync()会阻塞到完成
            ChannelFuture f = b.bind().sync();
            //阻塞当前线程，直到服务器的ServerChannel被关闭
            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully().sync();
        }
    }
}

EchoServerHandler

@ChannelHandler.Sharable
public class EchoServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf in = (ByteBuf)msg;
        System.out.println("Server accept: "+in.toString(CharsetUtil.UTF_8));
        ctx.writeAndFlush(in);
        //ctx.close();
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}