b.childHandler(new ChannelInitializer<SocketChannel>() {

            @Override

            protected void initChannel(SocketChannel ch) throws Exception {

                ByteBuf byteBuf = Unpooled.copiedBuffer("$_".getBytes());

                ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024,byteBuf));//自定义分割标识

                ch.pipeline().addLast(new StringDecoder()); //解码类，类似过滤器，处理类接收到数据就不用转到buf再转string了

                ch.pipeline().addLast(new MyServerHandler());

            }

        });

@Override

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

        //读取客户端发来的信息

        String m = (String) msg;

        System.out.println("client:"+m);

        //向客户端写信息

        String name="你好客户端：这是服务端返回的信息!$_";

        ctx.writeAndFlush(Unpooled.copiedBuffer(name.getBytes()));

    }

package com.lzh.netty;

import io.netty.bootstrap.Bootstrap;

import io.netty.buffer.ByteBuf;

import io.netty.buffer.Unpooled;

import io.netty.channel.ChannelFuture;

import io.netty.channel.ChannelInitializer;

import io.netty.channel.ChannelOption;

import io.netty.channel.EventLoopGroup;

import io.netty.channel.nio.NioEventLoopGroup;

import io.netty.channel.socket.SocketChannel;

import io.netty.channel.socket.nio.NioSocketChannel;

import io.netty.handler.codec.DelimiterBasedFrameDecoder;

import io.netty.handler.codec.string.StringDecoder;

/**

 * Created by 敲代码的卡卡罗特

 * on 2018/8/12 21:46.

 */

public class Client {

    public static void main(String[] arg){

        /**

         * 如果你只指定了一个EventLoopGroup，

         * 那他就会即作为一个‘boss’线程，

         * 也会作为一个‘workder’线程，

         * 尽管客户端不需要使用到‘boss’线程。

         */

        Bootstrap b = new Bootstrap(); // (1)

        EventLoopGroup workerGroup = new NioEventLoopGroup();

        b.group(workerGroup); // (2)

        b.channel(NioSocketChannel.class); // (3)

        b.option(ChannelOption.SO_KEEPALIVE, true); // (4)

        b.handler(new ChannelInitializer<SocketChannel>() {

            @Override

            public void initChannel(SocketChannel ch) throws Exception {

                ByteBuf byteBuf = Unpooled.copiedBuffer("$_".getBytes());

                ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024,byteBuf));//自定义分割标识

                ch.pipeline().addLast(new StringDecoder()); //解码类

                ch.pipeline().addLast(new MyClientHandler());

            }

        });

        try {

            ChannelFuture f = b.connect("127.0.0.1", 8888).sync();

            //向服务端发送信息

            f.channel().writeAndFlush(Unpooled.copiedBuffer("你好$_哈哈$_".getBytes()));

            f.channel().closeFuture().sync();

        } catch (InterruptedException e) {

            e.printStackTrace();

        } finally {

            workerGroup.shutdownGracefully();

        }

    }

}

package com.lzh.netty;

import io.netty.buffer.ByteBuf;

import io.netty.channel.ChannelHandlerAdapter;

import io.netty.channel.ChannelHandlerContext;

import io.netty.util.CharsetUtil;

import io.netty.util.ReferenceCountUtil;

/**

 * Created by 敲代码的卡卡罗特

 * on 2018/8/12 21:49.

 */

public class MyClientHandler extends ChannelHandlerAdapter {

    @Override

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

        try {

            //读取服务端发来的信息

            String m = (String) msg; // ByteBuf是netty提供的

            System.out.println("client:"+m);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            //当没有写操作的时候要把msg给清空。如果有写操作，就不用清空，因为写操作会自动把msg清空。这是netty的特性。

            ReferenceCountUtil.release(msg);

        }

    }

    @Override

    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {

        cause.printStackTrace();

        ctx.close();

    }

}

 ch.pipeline().addLast(new FixedLengthFrameDecoder(5)); //定长的分隔符