netty是一种NIO框架，对NIO进行了封装，让NIO使用起来更简便。
推荐学习文章：http://ifeve.com/netty5-user-guide/

Client：

public class Client {

    public static void main(String[] args) throws Exception {

        EventLoopGroup workgroup = new NioEventLoopGroup();
        Bootstrap b = new Bootstrap();
        b.group(workgroup)
        .channel(NioSocketChannel.class)
        .handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(new ClientHandler());
            }
        });

        ChannelFuture cf1 = b.connect("127.0.0.1", 8765).sync();

        //buf
        cf1.channel().writeAndFlush(Unpooled.copiedBuffer("777".getBytes()));

        cf1.channel().closeFuture().sync();
        workgroup.shutdownGracefully();

    }
}

ClientHandler:

public class ClientHandler extends ChannelHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        try {
            //do something msg
            ByteBuf buf = (ByteBuf)msg;
            byte[] data = new byte[buf.readableBytes()];
            buf.readBytes(data);
            String request = new String(data, "utf-8");
            System.out.println("Client: " + request);


        } finally {
            ReferenceCountUtil.release(msg);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

Server:

public class Server {

    public static void main(String[] args) throws Exception {
        //1 第一个线程组 是用于接收Client端连接的
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        //2 第二个线程组 是用于实际的业务处理操作的
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        //3 创建一个辅助类Bootstrap，就是对我们的Server进行一系列的配置
        ServerBootstrap b = new ServerBootstrap(); 
        //把俩个工作线程组加入进来
        b.group(bossGroup, workerGroup)
        //我要指定使用NioServerSocketChannel这种类型的通道
         .channel(NioServerSocketChannel.class)
        //一定要使用 childHandler 去绑定具体的 事件处理器
         .childHandler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(new ServerHandler());
            }
        });

        //绑定指定的端口 进行监听
        ChannelFuture f = b.bind(8765).sync(); 

        //Thread.sleep(1000000);
        f.channel().closeFuture().sync();

        bossGroup.shutdownGracefully();
        workerGroup.shutdownGracefully();



    }

}

ServerHandler:

public class ServerHandler  extends ChannelHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

            //do something msg
            ByteBuf buf = (ByteBuf)msg;
            byte[] data = new byte[buf.readableBytes()];
            buf.readBytes(data);
            String request = new String(data, "utf-8");
            System.out.println("Server: " + request);
            //写给客户端
            String response = "我是反馈的信息";
            ctx.writeAndFlush(Unpooled.copiedBuffer("888".getBytes()));
            //.addListener(ChannelFutureListener.CLOSE);


    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }

}