Netty进阶——粘包与半包（固定长度方式解决粘包问题）

Posted 2023-01-09 小志的博客

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一、固定长度方式解决粘包问题（代码示例）

1.1、固定长度方式解决粘包问题的服务端代码示例

让所有数据包长度固定（假设长度为 16 字节），服务器端加入
```
ch.pipeline().addLast(new FixedLengthFrameDecoder(16));
```

服务端完整代码示例

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.codec.FixedLengthFrameDecoder;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;

/**
 * @description: 固定长度方式解决粘包 问题服务端示例
 * @author: xz
 */
@Slf4j
public class NettyFixLengthServer 
    public static void main(String[] args) 
        new NettyFixLengthServer().start();
    

    void start() 
        NioEventLoopGroup boss = new NioEventLoopGroup(1);
        NioEventLoopGroup worker = new NioEventLoopGroup();
        try 
            ServerBootstrap serverBootstrap = new ServerBootstrap()
                    .channel(NioServerSocketChannel.class)
                     //调整 netty 的接受缓冲区（byteBuf）
                    .childOption(ChannelOption.RCVBUF_ALLOCATOR,new AdaptiveRecvByteBufAllocator(16,16,16))
                    .group(boss, worker)
                    .childHandler(new ChannelInitializer<SocketChannel>() 
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception 
                            //设置定长解码器，位置必须再LoggingHandler之前，作用让所有数据包长度固定（假设长度为 16 字节）
                            ch.pipeline().addLast(new FixedLengthFrameDecoder(16));
                            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
                                @Override
                                public void channelActive(ChannelHandlerContext ctx) throws Exception 
                                    log.debug("connected>>>>>>>>>>>>>>>> ", ctx.channel());
                                    super.channelActive(ctx);
                                
                                @Override
                                public 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");

1.2、固定长度方式解决粘包问题的客户端代码示例

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 io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;

import java.util.Arrays;
import java.util.Random;

/**
 * @description: 固定长度方式解决粘包 问题客户端示例
 * @author: xz
 */
@Slf4j
public class NettyFixLengthClient 
    public static void main(String[] args) 
        send();
    

    //剩余位置用下划线填充
    public static byte[] fill10Bytes(char c,int len)
        byte[] bytes = new byte[16];
        Arrays.fill(bytes, (byte) '_');
        for (int i = 0; i < len; i++) 
            bytes[i] = (byte) c;
        
        System.out.println(new String(bytes));
        return bytes;
    

    private static void send() 
        NioEventLoopGroup worker = new NioEventLoopGroup();
        try 
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.group(worker);
            bootstrap.handler(new ChannelInitializer<SocketChannel>() 
                @Override
                protected void initChannel(SocketChannel ch) throws Exception 
                    log.debug("connetted...");
                    ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
                    ch.pipeline().addLast(new ChannelInboundHandlerAdapter() 
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) throws Exception 
                            log.debug("sending...");
                            //设置ByteBuf
                            ByteBuf buffer = ctx.alloc().buffer();
                            // 发送内容随机的数据包
                            Random r = new Random();
                            char c = '0';
                            for (int i = 0; i < 10; i++) 
                                //剩余位置用下划线填充方法
                                byte[] bytes =fill10Bytes(c,r.nextInt(16)+1);
                                c++;
                                //写入到ByteBuf
                                buffer.writeBytes(bytes);
                            
                            ctx.writeAndFlush(buffer);
                        
                    );
                
            );
            ChannelFuture channelFuture = bootstrap.connect("localhost", 8080).sync();
            channelFuture.channel().closeFuture().sync();

         catch (InterruptedException e) 
            log.error("client error", e);
         finally 
            worker.shutdownGracefully();