Netty进阶——粘包与半包（预设长度方式解决粘包问题）

Posted 2023-01-12 小志的博客

tags:

篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了Netty进阶——粘包与半包（预设长度方式解决粘包问题）相关的知识，希望对你有一定的参考价值。

一、预设长度方式解决粘包问题（代码示例）

1.1、预设长度方式解决粘包问题的服务端代码示例

在发送消息前，先约定用定长字节表示接下来数据的长度，服务端加入如下代码：

//设置LTC解码器，4个参数分别为 最大长度，长度偏移，长度占用字节，长度调整，剥离字节数
ch.pipeline().addLast(new LengthFieldBasedFrameDecoder(1024, 0, 1, 0, 1));

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

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

    void start() 
        NioEventLoopGroup boss = new NioEventLoopGroup();
        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LTC解码器，4个参数分别为 最大长度，长度偏移，长度占用字节，长度调整，剥离字节数
                            ch.pipeline().addLast(new LengthFieldBasedFrameDecoder(1024, 0, 1, 0, 1));
                            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、预设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.Random;
/**
 * @description: 预设长度方式解决粘包 问题客户端示例
 * @author: xz
 */
@Slf4j
public class NerrtPresetLengthClient 
    public static void main(String[] args) 
        send();
    

    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) 
                    log.debug("connetted...");
                    ch.pipeline().addLast(new LoggingHandler(LogLevel.DEBUG));
                    ch.pipeline().addLast(new ChannelInboundHandlerAdapter() 
                        // 会在连接 channel 建立成功后，会触发 active 事件
                        @Override
                        public void channelActive(ChannelHandlerContext ctx) 
                            log.debug("sending...");
                            ByteBuf buf = ctx.alloc().buffer();
                            char c = 'a';
                            Random r = new Random();
                            for (int i = 0; i < 10; i++) 
                                byte length = (byte) (r.nextInt(16) + 1);
                                // 先写入长度
                                buf.writeByte(length);
                                // 再写入数据
                                for (int j = 1; j <= length; j++) 
                                    buf.writeByte((byte) c);
                                
                                c++;
                            
                            ctx.writeAndFlush(buf);
                        
                    );
                
            );
            ChannelFuture channelFuture = bootstrap.connect("localhost", 8080).sync();
            channelFuture.channel().closeFuture().sync();
         catch (InterruptedException e) 
            log.error("client error", e);
         finally 
            worker.shutdownGracefully();