2.Netty的粘包、拆包（一）

时间：2024-01-21 22:17:05

Netty粘包、拆包

1.什么是拆包、粘包

（1）拆包、粘包介绍

TCP是个“流”协议，所谓流，就是没有界限的一串数据。大家可以想想河里的流水，是连成一片的，其间并没有分界线。TCP底层并不了解上层业务数据的具体含义，它会根据TCP缓冲区的实际情况进行包的划分，所以在业务上认为，一个完整的包可能会被TCP拆分成多个包进行发送，也有可能把多个小的包封装成一个大的数据包发送，这就是所谓的TCP粘包和拆包问题。

（2）图解

（3）代码模拟

  1. 服务端Server

    package com.xm.netty.demo02;

import java.net.InetSocketAddress;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

public class Server {

 private final int port;

 public Server(int port) {
     this.port = port;
 }



 public static void main(String[] args) {

     int port = 8989;
     try {
         new Server(port).start();
     } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }

 }



 private void start() throws InterruptedException {
     EventLoopGroup g1 = new NioEventLoopGroup();
     EventLoopGroup g2 = new NioEventLoopGroup();
     try {
         ServerBootstrap bootstrap = new ServerBootstrap();
          bootstrap
                 .group(g1,g2)
                 .channel(NioServerSocketChannel.class)
                 .localAddress(new InetSocketAddress( port))
                 .childHandler(new ChannelInitializer() {
                     @Override
                     protected void initChannel(Channel ch) throws Exception {
                         ch.pipeline().addLast(new ServerHandler());
                     }
                 });
          ChannelFuture future = bootstrap.bind().sync();
          future.channel().closeFuture().sync();
     } finally {
         g1.shutdownGracefully().sync();
         g2.shutdownGracefully().sync();
     }
 }

}

  2. 服务端ServerHandler

    package com.xm.netty.demo02;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.CharsetUtil;

public class ServerHandler extends ChannelHandlerAdapter {

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

     ByteBuf in = (ByteBuf) msg;
     String str = in.toString(CharsetUtil.UTF_8);
     System.out.println("Server:"+str);
     str = "服务器返回--->"+ str;
     ctx.writeAndFlush(Unpooled.copiedBuffer(str.getBytes()));
 }

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

 @Override
 public void channelActive(ChannelHandlerContext ctx) throws Exception {
     System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"一个客户端连接!");
 }


}

  3. 客户端Client

    package com.xm.netty.demo02;


import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;

public class Client {

 private final int port;
 private final String host;



 public Client(int port, String host) {
     this.port = port;
     this.host = host;
 }

 public static void main(String[] args) {
     String host = "127.0.0.1";
     int port = 8989;
     try {
         new Client(port, host).start();
     } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }
 }

 private void start() throws InterruptedException {

     EventLoopGroup group = new NioEventLoopGroup();
     try {
         Bootstrap bootstrap = new Bootstrap();
         bootstrap
                 .group(group)
                 .channel(NioSocketChannel.class)
                 .remoteAddress(host, port)
                 .handler(new ChannelInitializer<SocketChannel>() {

                     @Override
                     protected void initChannel(SocketChannel ch) throws Exception {
                         ch.pipeline().addLast(new ClientHandler());
                     }

                 });

         ChannelFuture future = bootstrap.connect().sync();

         for(int i=10;i<20;i++) {
             String str = DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now()) + "---- " +i+"<<<";
             future.channel().writeAndFlush(Unpooled.copiedBuffer(str.getBytes()));
         }




         future.channel().closeFuture().sync();
     } finally {
         group.shutdownGracefully().sync();
     }

 }

}

  4. 客户端ClientHandler

    package com.xm.netty.demo02;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.CharsetUtil;
import io.netty.util.ReferenceCountUtil;

public class ClientHandler extends ChannelHandlerAdapter {

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


     try {

         ByteBuf in = (ByteBuf) msg;
         String str = in.toString(CharsetUtil.UTF_8);
         System.out.println("Client:"+str);

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

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

 @Override
 public void channelActive(ChannelHandlerContext ctx) throws Exception {
     System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"  已连接上服务器！");
 }


}

  5. 添加依赖

  6. 预期结果

    1）服务器

    2018-10-11T18:37:19.857一个客户端连接!

    Server:2018-10-11T18:37:19.855---- 10<<<

    Server:2018-10-11T18:37:20.377---- 11<<<

    Server:2018-10-11T18:37:20.877---- 12<<<

    Server:2018-10-11T18:37:21.378---- 13<<<

    Server:2018-10-11T18:37:21.879---- 14<<<

    Server:2018-10-11T18:37:22.379---- 15<<<

    Server:2018-10-11T18:37:22.879---- 16<<<

    Server:2018-10-11T18:37:23.38---- 17<<<

    Server:2018-10-11T18:37:23.881---- 18<<<

    Server:2018-10-11T18:37:24.382---- 19<<<

    （2）客户端

    2018-10-11T18:37:19.855 已连接上服务器！

    Client:服务器返回--->2018-10-11T18:37:19.855---- 10<<<

    Client:服务器返回--->2018-10-11T18:37:20.377---- 11<<<

    Client:服务器返回--->2018-10-11T18:37:20.877---- 12<<<

    Client:服务器返回--->2018-10-11T18:37:21.378---- 13<<<

    Client:服务器返回--->2018-10-11T18:37:21.879---- 14<<<

    Client:服务器返回--->2018-10-11T18:37:22.379---- 15<<<

    Client:服务器返回--->2018-10-11T18:37:22.879---- 16<<<

    Client:服务器返回--->2018-10-11T18:37:23.38---- 17<<<

    Client:服务器返回--->2018-10-11T18:37:23.881---- 18<<<

    Client:服务器返回--->2018-10-11T18:37:24.382---- 19<<<

  7. 实际结果

    （1）服务器

    2018-10-11T18:35:40.988一个客户端连接!
    Server:2018-10-11T18:35:40.986---- 10<<<2018-10-11T18:35:41.01---- 11<<<2018-10-11T18:35:41.01---- 12<<<2018-10-11T18:35:41.01---- 13<<<2018-10-11T18:35:41.01---- 14<<<2018-10-11T18:35:41.01---- 15<<<2018-10-11T18:35:41.01---- 16<<<2018-10-11T18:35:41.01---- 17<<<2018-10-11T18:35:41.01---- 18<<<2018-10-11T18:35:41.01---- 19<<<

    （2）客户端

    2018-10-11T18:35:40.986 已连接上服务器！
    Client:服务器返回--->2018-10-11T18:35:40.986---- 10<<<2018-10-11T18:35:41.01---- 11<<<2018-10-11T18:35:41.01---- 12<<<2018-10-11T18:35:41.01---- 13<<<2018-10-11T18:35:41.01---- 14<<<2018-10-11T18:35:41.01---- 15<<<2018-10-11T18:35:41.01---- 16<<<2018-10-11T18:35:41.01---- 17<<<2018-10-11T18:35:41.01---- 18<<<2018-10-11T18:35:41.01---- 19<<<

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