目录

• • 一、消息粘包和消息半包的概述
  • • 1.1、消息粘包
    • 1.2、消息半包
  • 二、粘包现象代码示例
  • • 2.1、粘包现象服务端示例代码
    • 2.2、粘包现象客户端示例代码
    • 2.3、分别启动服务端，客户端，查看服务端结果输出
  • 三、半包现象代码示例
  • • 3.1、半包现象服务端示例代码
    • 3.2、半包现象客户端示例代码
    • 3.3、分别启动服务端，客户端，查看服务端结果输出

一、消息粘包和消息半包的概述

1.1、消息粘包

• 当缓冲区足够大，由于网络不稳定种种原因，可能会有多条消息从通道读入缓冲区，此时如果无法分清数据包之间的界限，就会导致粘包问题。

1.2、消息半包

• 若消息没有接收完，缓冲区就被填满了，会导致从缓冲区取出的消息不完整，即半包的现象。

二、粘包现象代码示例

2.1、粘包现象服务端示例代码

• 服务端代码

  package com.example.nettytest.netty.day5;import io.netty.bootstrap.ServerBootstrap;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandlerAdapter;
  import io.netty.channel.ChannelInitializer;
  import io.netty.channel.nio.NioEventLoopGroup;
  import io.netty.channel.socket.SocketChannel;
  import io.netty.channel.socket.nio.NioServerSocketChannel;
  import io.netty.handler.logging.LogLevel;
  import io.netty.handler.logging.LoggingHandler;
  import lombok.extern.slf4j.Slf4j;/*** @description:   Netty粘包现象演示服务端*                 消息粘包：当缓冲区足够大，由于网络不稳定种种原因，可能会有多条消息从通道读入缓冲区，*                         此时如果无法分清数据包之间的界限，就会导致粘包问题；* @author: xz*/
  @Slf4j
  public class NettyServerTest {public static void main(String[] args) {new NettyServerTest().start();}void start() {NioEventLoopGroup boss = new NioEventLoopGroup(1);NioEventLoopGroup worker = new NioEventLoopGroup();try {ServerBootstrap serverBootstrap = new ServerBootstrap().channel(NioServerSocketChannel.class).group(boss, worker).childHandler(new ChannelInitializer() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {//会在连接channel建立成功后，触发active事件@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {log.debug("connected>>>>>>>>>>>>>>>> {}", ctx.channel());super.channelActive(ctx);}@Overridepublic void channelInactive(ChannelHandlerContext ctx) throws Exception {log.debug("disconnect>>>>>>>>>>>>>>>> {}", ctx.channel());super.channelInactive(ctx);}});}});ChannelFuture channelFuture = serverBootstrap.bind(8080);log.debug("{}>>>>>>>>>>>>>>>> binding...", channelFuture.channel());channelFuture.sync();log.debug("{}>>>>>>>>>>>>>>>> bound...", channelFuture.channel());channelFuture.channel().closeFuture().sync();} catch (InterruptedException e) {log.error("server error", e);} finally {boss.shutdownGracefully();worker.shutdownGracefully();log.debug(">>>>>>>>>>>>>>>>stoped");}}
  }
  

2.2、粘包现象客户端示例代码

• 客户端代码示例

  package com.example.nettytest.netty.day5;import io.netty.bootstrap.Bootstrap;
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandlerAdapter;
  import io.netty.channel.ChannelInitializer;
  import io.netty.channel.nio.NioEventLoopGroup;
  import io.netty.channel.socket.SocketChannel;
  import io.netty.channel.socket.nio.NioSocketChannel;
  import lombok.extern.slf4j.Slf4j;
  /*** @description: Netty粘包现象演示客户端* @author: xz*/
  @Slf4j
  public class NettyClientTest {public static void main(String[] args) {new NettyClientTest().start();}void start() {NioEventLoopGroup worker = new NioEventLoopGroup();try {Bootstrap bootstrap = new Bootstrap().channel(NioSocketChannel.class).group(worker).handler(new ChannelInitializer() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {log.debug("connetted》》》》》》》》》》》》》》》");ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {//会在连接channel建立成功后，触发active事件@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {log.debug("遍历 sending 每次发送16个字节》》》》》》》》》》》》》》》");for (int i = 0; i < 10; i++) {//设置缓冲区大小16个字节ByteBuf buffer = ctx.alloc().buffer(16);buffer.writeBytes(new byte[]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16});ctx.writeAndFlush(buffer);}}});}});ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 8080).sync();channelFuture.channel().closeFuture().sync();} catch (InterruptedException e) {log.error("client error", e);} finally {worker.shutdownGracefully();}}
  }
  

2.3、分别启动服务端，客户端，查看服务端结果输出

• 先启动服务端
  
• 再启动客户端
  
• 再次查看服务端
  注：可下图输出结果可知：服务器端的某次输出，可以看到一次就接收了 160 个字节，而非分 10 次接收。

三、半包现象代码示例

3.1、半包现象服务端示例代码

• 为现象明显，服务端添加一下接收缓冲区，其它代码不变

  serverBootstrap.option(ChannelOption.SO_RCVBUF, 10);
  

• 服务端完整示例代码

  package com.example.nettytest.netty.day5;import io.netty.bootstrap.ServerBootstrap;
  import io.netty.channel.*;
  import io.netty.channel.nio.NioEventLoopGroup;
  import io.netty.channel.socket.SocketChannel;
  import io.netty.channel.socket.nio.NioServerSocketChannel;
  import io.netty.handler.logging.LogLevel;
  import io.netty.handler.logging.LoggingHandler;
  import lombok.extern.slf4j.Slf4j;
  /*** @description:   Netty半包现象演示服务端*                 消息半包：若消息没有接收完，缓冲区就被填满了，会导致从缓冲区取出的消息不完整，即半包的现象。* @author: xz*/
  @Slf4j
  public class NettyServerTest1 {public static void main(String[] args) {new NettyServerTest().start();}void start() {NioEventLoopGroup boss = new NioEventLoopGroup(1);NioEventLoopGroup worker = new NioEventLoopGroup();try {ServerBootstrap serverBootstrap = new ServerBootstrap().channel(NioServerSocketChannel.class)//服务端添加接收缓冲区，大小设置10.option(ChannelOption.SO_RCVBUF, 10).group(boss, worker).childHandler(new ChannelInitializer() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {log.debug("connected================== {}", ctx.channel());super.channelActive(ctx);}@Overridepublic void channelInactive(ChannelHandlerContext ctx) throws Exception {log.debug("disconnect================== {}", ctx.channel());super.channelInactive(ctx);}});}});ChannelFuture channelFuture = serverBootstrap.bind(8080);log.debug("{} binding====================", channelFuture.channel());channelFuture.sync();log.debug("{} bound====================", channelFuture.channel());channelFuture.channel().closeFuture().sync();} catch (InterruptedException e) {log.error("server error", e);} finally {boss.shutdownGracefully();worker.shutdownGracefully();log.debug("stoped======================");}}
  }
  

3.2、半包现象客户端示例代码

• 客户端代码示例无变化，完整代码如下

  package com.example.nettytest.netty.day5;import io.netty.bootstrap.Bootstrap;
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandlerAdapter;
  import io.netty.channel.ChannelInitializer;
  import io.netty.channel.nio.NioEventLoopGroup;
  import io.netty.channel.socket.SocketChannel;
  import io.netty.channel.socket.nio.NioSocketChannel;
  import lombok.extern.slf4j.Slf4j;
  /*** @description: Netty半包现象演示客户端* @author: xz*/
  @Slf4j
  public class NettyClientTest1 {public static void main(String[] args) {new NettyClientTest1().start();}void start() {NioEventLoopGroup worker = new NioEventLoopGroup();try {Bootstrap bootstrap = new Bootstrap().channel(NioSocketChannel.class).group(worker).handler(new ChannelInitializer() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {log.debug("connetted----------------");ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {//会在连接channel建立成功后，触发active事件@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {log.debug("sending----------------");for (int i = 0; i < 10; i++) {ByteBuf buffer = ctx.alloc().buffer(16);buffer.writeBytes(new byte[]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16});ctx.writeAndFlush(buffer);}}});}});ChannelFuture channelFuture = bootstrap.connect("127.0.0.1", 8080).sync();channelFuture.channel().closeFuture().sync();} catch (InterruptedException e) {log.error("client error", e);} finally {worker.shutdownGracefully();}}
  }
  

3.3、分别启动服务端，客户端，查看服务端结果输出

• 先启动服务端
  
• 再启动客户端
  
• 再次查看服务端
  注：可下图输出结果可知：服务器端的某次输出，可以看到接收的消息被分为两节，第一次 16 字节，第二次 32 字节，第三次 64 字节，第四次 48 字节