AI 助理
备案控制台
开发者社区 开发与运维 文章 正文

【Netty】TCP粘包和拆包

2022-05-05 146
版权
版权声明：
本文内容由阿里云实名注册用户自发贡献，版权归原作者所有，阿里云开发者社区不拥有其著作权，亦不承担相应法律责任。具体规则请查看《 阿里云开发者社区用户服务协议》和 《阿里云开发者社区知识产权保护指引》。如果您发现本社区中有涉嫌抄袭的内容，填写 侵权投诉表单进行举报，一经查实，本社区将立刻删除涉嫌侵权内容。
简介： 前面已经基本上讲解完了Netty的主要内容，现在来学习Netty中的一些可能存在的问题，如TCP粘包和拆包。

一、前言

　　前面已经基本上讲解完了Netty的主要内容，现在来学习Netty中的一些可能存在的问题，如TCP粘包和拆包。


二、粘包和拆包

　　对于TCP协议而言，当底层发送消息和接受消息时，都需要考虑TCP的粘包和拆包问题，一个完整的数据包可能会被TCP拆分为多个包发送，或者将多个小的数据包封装成大的数据包发送。

　　2.1 粘包和拆包基础

　　假设客户端发送D1和D2两个数据包至服务端，由于服务端每次读取的数据大小时不确定的，因此，可能存在如下四种情况。

　　1.png

　　① 服务端分两次读取到数据包，分别为D1和D2，没有粘包和拆包。

　　② 服务端一次读取两个数据包D1和D2，D1和D2黏合在一起，称为TCP粘包。

　　③ 服务端一次读取完整的D1数据包和D2数据包的一部分，第二次读取D2剩余的部分，称为TCP拆包。

　　④ 服务端一次读取D1数据包的一部分，第二次读取D1的剩余部分和D2数据包。

　　可以看到，在底层发送数据时，可能会发生粘包和拆包，其原因大致有如下三种。

　　① 应用程序写入字节大小大于套接字缓冲区大小。

　　② 进行MSS（Max Segment Size）大小的TCP分段。

　　③ 以太网帧的负载大于MTU（Maximum Transmission Unit）进行分片。

　　由于底层的TCP协议无法理解上层的业务数据，所以底层无法保证数据不被拆分和重组，而为了解决粘包问题，业界主要的策略如下。

　　① 消息定长，如每个报文大小固定为200个字节，如果不够，空格补位。

　　② 在包尾添加回车换行符进行分割，如FTP协议。

　　③ 将消息划分为消息头和消息体，消息头中包含消息总长度的字段。

　　2.2 TCP粘包示例

　　下面通过一个示例展示未考虑粘包问题导致的异常。

　　1. TimeServerHandler　

package com.hust.grid.leesf.chapter4;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
/**
 * Created by Leesf on 2017/6/28.
 */
public class TimeServerHandler extends ChannelInboundHandlerAdapter {
    private int counter;
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8").substring(0, req.length
                - System.getProperty("line.separator").length());
        System.out.println("The time server receive order : " + body
                + " ; the counter is : " + ++counter);
        String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new java.util.Date(
                System.currentTimeMillis()).toString() : "BAD ORDER";
        currentTime = currentTime + System.getProperty("line.separator");
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.writeAndFlush(resp);
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

　2. TimeServer

package com.hust.grid.leesf.chapter4;
import io.netty.bootstrap.ServerBootstrap;
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.NioServerSocketChannel;
/**
 * Created by Leesf on 2017/6/28.
 */
public class TimeServer {
    public void bind(int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    .childHandler(new ChildChannelHandler());
            ChannelFuture f = b.bind(port).sync();
            f.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
    private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
        @Override
        protected void initChannel(SocketChannel arg0) throws Exception {
            arg0.pipeline().addLast(new TimeServerHandler());
        }
    }
    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                // ignore
            }
        }
        new TimeServer().bind(port);
    }
}

3. TimeClientHandler　

package com.hust.grid.leesf.chapter4;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import java.util.logging.Logger;
/**
 * Created by Leesf on 2017/6/28.
 */
public class TimeClientHandler extends ChannelInboundHandlerAdapter {
    private static final Logger logger = Logger
            .getLogger(TimeClientHandler.class.getName());
    private int counter;
    private byte[] req;
    public TimeClientHandler() {
        req = ("QUERY TIME ORDER" + System.getProperty("line.separator"))
                .getBytes();
    }
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ByteBuf message = null;
        for (int i = 0; i < 100; i++) {
            message = Unpooled.buffer(req.length);
            message.writeBytes(req);
            ctx.writeAndFlush(message);
        }
    }
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("Now is : " + body + " ; the counter is : "
                + ++counter);
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

　4. TimeClient　

package com.hust.grid.leesf.chapter4;
import io.netty.bootstrap.Bootstrap;
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;
/**
 * Created by Leesf on 2017/6/28.
 */
public class TimeClient {
    public void connect(int port, String host) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch)
                                throws Exception {
                            ch.pipeline().addLast(new TimeClientHandler());
                        }
                    });
            ChannelFuture f = b.connect(host, port).sync();
            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }
    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                // ignore
            }
        }
        new TimeClient().connect(port, "127.0.0.1");
    }
}

分别运行服务器和客户端，其中服务器的运行结果如下：　

The time server receive order : QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORD ; the counter is : 1
The time server receive order : 
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER
QUERY TIME ORDER ; the counter is : 2

客户端的运行结果如下：

Now is : BAD ORDER
BAD ORDER
 ; the counter is : 1

可以看到服务端只接收到了两条消息，一条消息包含了57条指令，另一条包含了43条指令，其与我们设计的100条单独的消息不相符，发生了粘包。对于客户端而言，其收到了两条BAD ORDER，表示收到了两条消息，counter应该为2，但是其counter为1，表示也发生了粘包。

　　下面通过Netty的LineBasedFrameDecoder和String来解决粘包问题。

　　1. TimeServerHandler　

package com.hust.grid.leesf.chapter4.fault;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
/**
 * Created by Leesf on 2017/6/28.
 */
public class TimeServerHandler extends ChannelInboundHandlerAdapter {
    private int counter;
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8").substring(0, req.length
                - System.getProperty("line.separator").length());
        System.out.println("The time server receive order : " + body
                + " ; the counter is : " + ++counter);
        String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new java.util.Date(
                System.currentTimeMillis()).toString() : "BAD ORDER";
        currentTime = currentTime + System.getProperty("line.separator");
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.writeAndFlush(resp);
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

　2. TimeServer　

package com.hust.grid.leesf.chapter4.fault;
import io.netty.bootstrap.ServerBootstrap;
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.NioServerSocketChannel;
/**
 * Created by Leesf on 2017/6/28.
 */
public class TimeServer {
    public void bind(int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    .childHandler(new ChildChannelHandler());
            ChannelFuture f = b.bind(port).sync();
            f.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
    private class ChildChannelHandler extends ChannelInitializer<SocketChannel> {
        @Override
        protected void initChannel(SocketChannel arg0) throws Exception {
            arg0.pipeline().addLast(new TimeServerHandler());
        }
    }
    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                // ignore
            }
        }
        new TimeServer().bind(port);
    }
}

3. TimeClientHandler

package com.hust.grid.leesf.chapter4.correct;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import java.util.logging.Logger;
/**
 * Created by Leesf on 2017/6/28.
 */
public class TimeClientHandler extends ChannelInboundHandlerAdapter {
    private int counter;
    private byte[] req;
    public TimeClientHandler() {
        req = ("QUERY TIME ORDER" + System.getProperty("line.separator"))
                .getBytes();
    }
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ByteBuf message = null;
        for (int i = 0; i < 100; i++) {
            message = Unpooled.buffer(req.length);
            message.writeBytes(req);
            ctx.writeAndFlush(message);
        }
    }
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        String body = (String) msg;
        System.out.println("Now is : " + body + " ; the counter is : "
                + ++counter);
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

4. TimeClient

package com.hust.grid.leesf.chapter4.correct;
import io.netty.bootstrap.Bootstrap;
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.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
/**
 * Created by Leesf on 2017/6/28.
 */
public class TimeClient {
    public void connect(int port, String host) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch)
                                throws Exception {
                            ch.pipeline().addLast(
                                    new LineBasedFrameDecoder(1024));
                            ch.pipeline().addLast(new StringDecoder());
                            ch.pipeline().addLast(new TimeClientHandler());
                        }
                    });
            ChannelFuture f = b.connect(host, port).sync();
            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }
    public static void main(String[] args) throws Exception {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                // ignore
            }
        }
        new TimeClient().connect(port, "127.0.0.1");
    }
}

分别运行服务端和客户端，服务端结果如下：

"D:\Program Files (x86)\Java\jdk1.8.0_65\bin\java" "-javaagent:D:\Program Files (x86)\JetBrains\IntelliJ IDEA 2017.1.4\lib\idea_rt.jar=62564:D:\Program Files (x86)\JetBrains\IntelliJ IDEA 2017.1.4\bin" -Dfile.encoding=UTF-8 -classpath "D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\charsets.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\deploy.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\access-bridge-64.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\cldrdata.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\dnsns.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\jaccess.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\jfxrt.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\localedata.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\nashorn.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\sunec.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\sunjce_provider.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\sunmscapi.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\sunpkcs11.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\zipfs.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\javaws.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\jce.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\jfr.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\jfxswt.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\jsse.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\management-agent.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\plugin.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\resources.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\rt.jar;F:\01_Code\02_Idea\CoreInNetty\target\classes;C:\Users\lsf\.m2\repository\io\netty\netty-all\4.0.32.Final\netty-all-4.0.32.Final.jar;C:\Users\lsf\.m2\repository\com\fasterxml\jackson\core\jackson-core\2.6.3\jackson-core-2.6.3.jar;C:\Users\lsf\.m2\repository\com\fasterxml\jackson\core\jackson-databind\2.6.3\jackson-databind-2.6.3.jar;C:\Users\lsf\.m2\repository\com\fasterxml\jackson\core\jackson-annotations\2.6.0\jackson-annotations-2.6.0.jar" com.hust.grid.leesf.chapter4.correct.TimeServer
The time server receive order : QUERY TIME ORDER ; the counter is : 1
The time server receive order : QUERY TIME ORDER ; the counter is : 2
The time server receive order : QUERY TIME ORDER ; the counter is : 3
The time server receive order : QUERY TIME ORDER ; the counter is : 4
The time server receive order : QUERY TIME ORDER ; the counter is : 5
The time server receive order : QUERY TIME ORDER ; the counter is : 6
The time server receive order : QUERY TIME ORDER ; the counter is : 7
The time server receive order : QUERY TIME ORDER ; the counter is : 8
The time server receive order : QUERY TIME ORDER ; the counter is : 9
The time server receive order : QUERY TIME ORDER ; the counter is : 10
The time server receive order : QUERY TIME ORDER ; the counter is : 11
The time server receive order : QUERY TIME ORDER ; the counter is : 12
The time server receive order : QUERY TIME ORDER ; the counter is : 13
The time server receive order : QUERY TIME ORDER ; the counter is : 14
The time server receive order : QUERY TIME ORDER ; the counter is : 15
The time server receive order : QUERY TIME ORDER ; the counter is : 16
The time server receive order : QUERY TIME ORDER ; the counter is : 17
The time server receive order : QUERY TIME ORDER ; the counter is : 18
The time server receive order : QUERY TIME ORDER ; the counter is : 19
The time server receive order : QUERY TIME ORDER ; the counter is : 20
The time server receive order : QUERY TIME ORDER ; the counter is : 21
The time server receive order : QUERY TIME ORDER ; the counter is : 22
The time server receive order : QUERY TIME ORDER ; the counter is : 23
The time server receive order : QUERY TIME ORDER ; the counter is : 24
The time server receive order : QUERY TIME ORDER ; the counter is : 25
The time server receive order : QUERY TIME ORDER ; the counter is : 26
The time server receive order : QUERY TIME ORDER ; the counter is : 27
The time server receive order : QUERY TIME ORDER ; the counter is : 28
The time server receive order : QUERY TIME ORDER ; the counter is : 29
The time server receive order : QUERY TIME ORDER ; the counter is : 30
The time server receive order : QUERY TIME ORDER ; the counter is : 31
The time server receive order : QUERY TIME ORDER ; the counter is : 32
The time server receive order : QUERY TIME ORDER ; the counter is : 33
The time server receive order : QUERY TIME ORDER ; the counter is : 34
The time server receive order : QUERY TIME ORDER ; the counter is : 35
The time server receive order : QUERY TIME ORDER ; the counter is : 36
The time server receive order : QUERY TIME ORDER ; the counter is : 37
The time server receive order : QUERY TIME ORDER ; the counter is : 38
The time server receive order : QUERY TIME ORDER ; the counter is : 39
The time server receive order : QUERY TIME ORDER ; the counter is : 40
The time server receive order : QUERY TIME ORDER ; the counter is : 41
The time server receive order : QUERY TIME ORDER ; the counter is : 42
The time server receive order : QUERY TIME ORDER ; the counter is : 43
The time server receive order : QUERY TIME ORDER ; the counter is : 44
The time server receive order : QUERY TIME ORDER ; the counter is : 45
The time server receive order : QUERY TIME ORDER ; the counter is : 46
The time server receive order : QUERY TIME ORDER ; the counter is : 47
The time server receive order : QUERY TIME ORDER ; the counter is : 48
The time server receive order : QUERY TIME ORDER ; the counter is : 49
The time server receive order : QUERY TIME ORDER ; the counter is : 50
The time server receive order : QUERY TIME ORDER ; the counter is : 51
The time server receive order : QUERY TIME ORDER ; the counter is : 52
The time server receive order : QUERY TIME ORDER ; the counter is : 53
The time server receive order : QUERY TIME ORDER ; the counter is : 54
The time server receive order : QUERY TIME ORDER ; the counter is : 55
The time server receive order : QUERY TIME ORDER ; the counter is : 56
The time server receive order : QUERY TIME ORDER ; the counter is : 57
The time server receive order : QUERY TIME ORDER ; the counter is : 58
The time server receive order : QUERY TIME ORDER ; the counter is : 59
The time server receive order : QUERY TIME ORDER ; the counter is : 60
The time server receive order : QUERY TIME ORDER ; the counter is : 61
The time server receive order : QUERY TIME ORDER ; the counter is : 62
The time server receive order : QUERY TIME ORDER ; the counter is : 63
The time server receive order : QUERY TIME ORDER ; the counter is : 64
The time server receive order : QUERY TIME ORDER ; the counter is : 65
The time server receive order : QUERY TIME ORDER ; the counter is : 66
The time server receive order : QUERY TIME ORDER ; the counter is : 67
The time server receive order : QUERY TIME ORDER ; the counter is : 68
The time server receive order : QUERY TIME ORDER ; the counter is : 69
The time server receive order : QUERY TIME ORDER ; the counter is : 70
The time server receive order : QUERY TIME ORDER ; the counter is : 71
The time server receive order : QUERY TIME ORDER ; the counter is : 72
The time server receive order : QUERY TIME ORDER ; the counter is : 73
The time server receive order : QUERY TIME ORDER ; the counter is : 74
The time server receive order : QUERY TIME ORDER ; the counter is : 75
The time server receive order : QUERY TIME ORDER ; the counter is : 76
The time server receive order : QUERY TIME ORDER ; the counter is : 77
The time server receive order : QUERY TIME ORDER ; the counter is : 78
The time server receive order : QUERY TIME ORDER ; the counter is : 79
The time server receive order : QUERY TIME ORDER ; the counter is : 80
The time server receive order : QUERY TIME ORDER ; the counter is : 81
The time server receive order : QUERY TIME ORDER ; the counter is : 82
The time server receive order : QUERY TIME ORDER ; the counter is : 83
The time server receive order : QUERY TIME ORDER ; the counter is : 84
The time server receive order : QUERY TIME ORDER ; the counter is : 85
The time server receive order : QUERY TIME ORDER ; the counter is : 86
The time server receive order : QUERY TIME ORDER ; the counter is : 87
The time server receive order : QUERY TIME ORDER ; the counter is : 88
The time server receive order : QUERY TIME ORDER ; the counter is : 89
The time server receive order : QUERY TIME ORDER ; the counter is : 90
The time server receive order : QUERY TIME ORDER ; the counter is : 91
The time server receive order : QUERY TIME ORDER ; the counter is : 92
The time server receive order : QUERY TIME ORDER ; the counter is : 93
The time server receive order : QUERY TIME ORDER ; the counter is : 94
The time server receive order : QUERY TIME ORDER ; the counter is : 95
The time server receive order : QUERY TIME ORDER ; the counter is : 96
The time server receive order : QUERY TIME ORDER ; the counter is : 97
The time server receive order : QUERY TIME ORDER ; the counter is : 98
The time server receive order : QUERY TIME ORDER ; the counter is : 99
The time server receive order : QUERY TIME ORDER ; the counter is : 100

客户端运行结果如下：

"D:\Program Files (x86)\Java\jdk1.8.0_65\bin\java" "-javaagent:D:\Program Files (x86)\JetBrains\IntelliJ IDEA 2017.1.4\lib\idea_rt.jar=62637:D:\Program Files (x86)\JetBrains\IntelliJ IDEA 2017.1.4\bin" -Dfile.encoding=UTF-8 -classpath "D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\charsets.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\deploy.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\access-bridge-64.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\cldrdata.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\dnsns.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\jaccess.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\jfxrt.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\localedata.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\nashorn.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\sunec.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\sunjce_provider.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\sunmscapi.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\sunpkcs11.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\ext\zipfs.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\javaws.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\jce.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\jfr.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\jfxswt.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\jsse.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\management-agent.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\plugin.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\resources.jar;D:\Program Files (x86)\Java\jdk1.8.0_65\jre\lib\rt.jar;F:\01_Code\02_Idea\CoreInNetty\target\classes;C:\Users\lsf\.m2\repository\io\netty\netty-all\4.0.32.Final\netty-all-4.0.32.Final.jar;C:\Users\lsf\.m2\repository\com\fasterxml\jackson\core\jackson-core\2.6.3\jackson-core-2.6.3.jar;C:\Users\lsf\.m2\repository\com\fasterxml\jackson\core\jackson-databind\2.6.3\jackson-databind-2.6.3.jar;C:\Users\lsf\.m2\repository\com\fasterxml\jackson\core\jackson-annotations\2.6.0\jackson-annotations-2.6.0.jar" com.hust.grid.leesf.chapter4.correct.TimeClient
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 1
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 2
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 3
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 4
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 5
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 6
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 7
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 8
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 9
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 10
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 11
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 12
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 13
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 14
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 15
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 16
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 17
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 18
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 19
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 20
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 21
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 22
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 23
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 24
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 25
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 26
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 27
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 28
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 29
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 30
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 31
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 32
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 33
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 34
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 35
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 36
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 37
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 38
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 39
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 40
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 41
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 42
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 43
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 44
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 45
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 46
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 47
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 48
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 49
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 50
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 51
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 52
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 53
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 54
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 55
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 56
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 57
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 58
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 59
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 60
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 61
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 62
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 63
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 64
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 65
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 66
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 67
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 68
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 69
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 70
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 71
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 72
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 73
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 74
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 75
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 76
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 77
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 78
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 79
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 80
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 81
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 82
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 83
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 84
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 85
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 86
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 87
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 88
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 89
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 90
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 91
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 92
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 93
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 94
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 95
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 96
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 97
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 98
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 99
Now is : Wed Jun 28 16:12:25 CST 2017 ; the counter is : 100

可以看到此时客户端和服务端的消息发送和接收都已经正常，不存在粘包问题。

　　2.3 LineBasedFrameDecoder和StringDecoder解码器说明

　　LineBasedFrameDecoder会依次遍历ByteBuf中的可读字节，判断是否有\n或者\r\n，其作为一行结束的标志，其是支持以换行符为结束标志的解码器，支持携带结束符和非结束符的两种解码方式，同时支持配置最大单行长度，此时，如果连续读取最大长度后仍未发现换行符，则会抛出异常，并忽略之前读取的数据。

　　StringDecoder将接收的对象转化为字符串，然后继续调用后面的handler，LineBasedFrameDecoder和StringDecoder组合起来使用用来解决按行切换的文本解码器。并且Netty中提供了丰富的解码器和编码器供使用，具体的可以参见官方文档。


三、总结

　　本篇博文讲解了TCP粘包，以及如何通过解码器解决TCP粘包问题，当然，Netty除了提供按行切换的文本解码器之外，还针对不同的应用场景，提供了其他丰富的解码器。谢谢各位园友的观看~

　

文章标签：
云数据库 ClickHouse
网络协议
移动开发
关键词：
Netty tcp
Netty粘包包
Netty粘包
Netty包
Netty拆包
xleesf
目录
相关文章
nanshaws
|
1月前
|
网络协议 前端开发
netty的TCP服务端和客户端实现
本文介绍了使用Netty框架实现TCP服务端和客户端的步骤，包括添加Netty依赖、编写服务端和客户端的代码，涉及NioEventLoopGroup、ServerBootstrap、Bootstrap、ChannelInitializer等核心组件，以及如何启动服务端监听和客户端连接。
nanshaws
139 4
萝卜丝丸子
|
3月前
|
编解码 网络协议 开发者
Netty运行原理问题之NettyTCP的粘包和拆包的问题如何解决
Netty运行原理问题之NettyTCP的粘包和拆包的问题如何解决
萝卜丝丸子
37 1
竹子爱熊猫
|
3月前
|
移动开发 网络协议 算法
(十)Netty进阶篇：漫谈网络粘包、半包问题、解码器与长连接、心跳机制实战
在前面关于《Netty入门篇》的文章中，咱们已经初步对Netty这个著名的网络框架有了认知，本章的目的则是承接上文，再对Netty中的一些进阶知识进行阐述，毕竟前面的内容中，仅阐述了一些Netty的核心组件，想要真正掌握Netty框架，对于它我们应该具备更为全面的认知。
竹子爱熊猫
193 2
码农阿豪
|
5月前
|
网络协议
netty粘包问题分析
netty粘包问题分析
码农阿豪
42 0
肥猪lele01
|
5月前
|
Java
Netty传输object并解决粘包拆包问题
Netty传输object并解决粘包拆包问题
肥猪lele01
49 0
Heron
|
网络协议 算法
Netty入门到超神系列-TCP粘包拆包处理
TCP是面向连接的，服务端和客户端通过socket进行数据传输，发送端为了更有效的发送数据，通常会使用Nagle算法把多个数据块合并成一个大的数据块，这样做虽然提高了效率，但是接收端就很难识别完整的数据包了(TCP无消息保护边界)，可能会出现粘包拆包的问题。
Heron
96 0
游客a74jvhcp7vclg
|
移动开发 网络协议
Netty解决TCP粘包/拆包的问题
首先要明确, 粘包问题中的 “包”, 是指应用层的数据包.在TCP的协议头中, 没有如同UDP一样的 “报文长度” 字段,但是有一个序号字段.
游客a74jvhcp7vclg
254 0
Netty解决TCP粘包/拆包的问题
松伯
|
网络协议 前端开发 Java
Netty的TCP粘包/拆包（源码二）
假设客户端分别发送了两个数据包D1和D2给服务器，由于服务器端一次读取到的字节数是不确定的，所以可能发生四种情况： 　　1、服务端分两次读取到了两个独立的数据包，分别是D1和D2，没有粘包和拆包。 　　2、服务端一次接收到了两个数据包，D1和D2粘合在一起，被称为TCP粘包。
松伯
1010 0
jsjsjjs
|
存储 缓存 NoSQL
跟着源码学IM(十一)：一套基于Netty的分布式高可用IM详细设计与实现(有源码)
本文将要分享的是如何从零实现一套基于Netty框架的分布式高可用IM系统，它将支持长连接网关管理、单聊、群聊、聊天记录查询、离线消息存储、消息推送、心跳、分布式唯一ID、红包、消息同步等功能，并且还支持集群部署。
jsjsjjs
13498 1
宁在春
|
6月前
|
消息中间件 Oracle Dubbo
Netty 源码共读（一）如何阅读JDK下sun包的源码
Netty 源码共读（一）如何阅读JDK下sun包的源码
宁在春
127 1