netty学习二（解决tcp/udp 粘包，拆包问题）

在通讯协议中，粘包，拆包是常发生的事情，而netty则很好的给出了三种解决方式，下面分别介绍：

一;利用LineBasedFrameDecoder解决TCP粘包问题

直接上代码，

Client类：

package stickorApartPackageResolveOne.one;

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;

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolveOne.one
 * @ClassName: Client
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/12 16:48
 * @Version: 1.0
 *  *LineBasedFrameDecoder以换行符为结束标志的解码器，支持携带结束符或者不携带结束符两种解码方式，
 *  * 同时支持配置单行的最大长度。如果连续读取到最大长度后仍然没有发现换行符，
 *  * 就会抛出异常，同时忽略掉之前读到的异常码流。
 *  * StringDecoder的功能非常简单，就是将接收到的对象转换成字符串，
 *  * 然后继续调用后面的handler。LineBasedFrameDecoder+StringDecoder组合就是按行切换的文本解码器，
 *  * 它被设计用来支持TCP的粘包和拆包。
 */
public class Client {

    public static void main(String[] args) {
        int port = 8080;
        String host = "127.0.0.1";
        new Client().connect(port, host);
    }

    private void connect(int port, String host) {


        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bst = new Bootstrap();
            bst.group(eventLoopGroup);
            bst.channel(NioSocketChannel.class);
            bst.option(ChannelOption.TCP_NODELAY, true);
            bst.handler(new ChannelInitializer() {
                @Override
                protected void initChannel(SocketChannel socketChannel) throws Exception {
                    socketChannel.pipeline().addLast(new LineBasedFrameDecoder(1024));
                    socketChannel.pipeline().addLast(new StringDecoder());
                    socketChannel.pipeline().addLast(new ClientHandler());
                }
            });
            ChannelFuture f = bst.connect(host, port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            eventLoopGroup.shutdownGracefully();
        }
    }
}

ClientHandler类

package stickorApartPackageResolveOne.one;

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

import java.util.logging.Logger;

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolveOne.one
 * @ClassName: ClientHandler
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/12 17:03
 * @Version: 1.0
 */
public class ClientHandler extends ChannelHandlerAdapter {

    private static final Logger logger = Logger
            .getLogger(ClientHandler.class.getName());

    private int counter;
    String req = ("QUERY TIME ORDER" + System.getProperty("line.separator")); 

   

    @Override
    public void channelActive(ChannelHandlerContext ctx) {                  for (int i = 0; i < 30; i++) {
                   ctx.writeAndFlush(Unpooled.copiedBuffer(req.getBytes()));
           }    }

    @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) {
        // 释放资源
        logger.warning("Unexpected exception from downstream : " + cause.getMessage());
        ctx.close();
    }
}

Server类

 

package stickorApartPackageResolveOne.one;

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;
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolveOne
 * @ClassName: Timeserver
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/12 16:03
 * @Version: 1.0
 */
public class Server {

    public static void main(String args[]) {
        int port = 8080;
        new Server().bind(port);
    }

    private void bind(int port) {

        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        EventLoopGroup eventLoopGroup1 = new NioEventLoopGroup();

        try {
            ServerBootstrap sbt = new ServerBootstrap();
            sbt.group(eventLoopGroup, eventLoopGroup1);
            sbt.channel(NioServerSocketChannel.class);
            sbt.option(ChannelOption.SO_BACKLOG, 1024);
            sbt.childHandler(new ChannelInitializer() {
                @Override
                protected void initChannel(SocketChannel socketChannel) throws Exception {
                    //利用LineBasedFrameDecoder解决TCP粘包问题
                    socketChannel.pipeline().addLast(new LineBasedFrameDecoder(1024));
                    socketChannel.pipeline().addLast(new StringDecoder());
                    socketChannel.pipeline().addLast(new ServerHandler());
                }
            });
            ChannelFuture cf = sbt.bind(port).sync();
            cf.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            eventLoopGroup.shutdownGracefully();
            eventLoopGroup1.shutdownGracefully();
        }

    }
}

ServerHandler类

package stickorApartPackageResolveOne.one;

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

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolveOne
 * @ClassName: ServerHandler
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/12 16:20
 * @Version: 1.0
 */
public class ServerHandler extends ChannelHandlerAdapter {

    int counter;

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        String body =  (String)msg;
        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) throws Exception {
        ctx.close();
    }


}

 

先直接上结果：

客户端：

服务端：

 

 LineBasedFrameDecoder和StringDecoder的原理分析

LineBasedFrameDecoder的工作原理是它依次遍历ByteBuf中的可读字节，判断看是否有＼n或者以\r\n气如果有，就以此位置为结束位置，从可读索引到结束位置区间的字节就组成了一行。它是以换行符为结束标志的解码器，支持携带结束符或者不携带结束符两种解码方式，同时支持配置单行的最大长度。如果连续读取到最大长度后仍然没有发现换行符，就会抛出异常，同时忽略掉之前读到的异常码流。
StringDecoder的功能非常简单，就是将接收到的对象转换成字符串，然后继续调用后面的handler。LineBasedFrameDecoder+StringDecoder组合就是按行切换的文本解码器，它被设计用来支持TCP的粘包和拆包。

 

二、利用DelimiterBasedFrameDecoder

Client1类：

package stickorApartPackageResolve.two;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
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.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolve.two
 * @ClassName: Client1
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/14 9:18
 * @Version: 1.0
 */
public class Client1 {

    public static void main(String[] args) {

        int port = 8080;
        String host = "127.0.0.1";
        new Client1().connect(host,port);

    }

    private void connect(String host, int port) {

        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();

        try {
            Bootstrap bs = new Bootstrap();
            bs.group(eventLoopGroup);
            bs.channel(NioSocketChannel.class);
            bs.option(ChannelOption.TCP_NODELAY, true);
            bs.handler(new ChannelInitializer() {
                @Override
                protected void initChannel(SocketChannel socketChannel) throws Exception {
                    ByteBuf buffer = Unpooled.copiedBuffer("$_".getBytes());
                    socketChannel.pipeline().addLast(new DelimiterBasedFrameDecoder(1024,buffer));
                    socketChannel.pipeline().addLast(new StringDecoder());
                    socketChannel.pipeline().addLast(new Client1Handler());
                }
            });
            ChannelFuture f = bs.connect(host,port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            eventLoopGroup.shutdownGracefully();
        }
    }
}

Client1Handler类

package stickorApartPackageResolve.two;

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolve.two
 * @ClassName: Client1Handler
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/14 14:35
 * @Version: 1.0
 */
public class Client1Handler extends ChannelHandlerAdapter {

    private int counter;
    private String req = "Hi,XXX! Welcome to netty.$_";

    @Override
    public void channelActive(ChannelHandlerContext ctx){
        for(int i=0; i<10; i++){
            ctx.writeAndFlush(Unpooled.copiedBuffer(req.getBytes()));
        }
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg){
        String body = (String) msg;
        System.out.println("this is : " + ++counter + "time recive " + body);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // 释放资源
        ctx.close();
    }
}

Server1类

package stickorApartPackageResolve.two;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
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;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolve.two
 * @ClassName: Server1
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/14 8:54
 * @Version: 1.0
 */
public class Server1 {
    public static void main(String[] args) {
        int port = 8080;
        new Server1().bind(port);
    }

    private void bind(int port) {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        EventLoopGroup eventLoopGroup1 = new NioEventLoopGroup();

        try {
            ServerBootstrap sbt = new ServerBootstrap();
            sbt.group(eventLoopGroup,eventLoopGroup1);
            sbt.channel(NioServerSocketChannel.class);
            sbt.option(ChannelOption.SO_BACKLOG, 1024);
            sbt.childHandler(new ChannelInitializer() {
                @Override
                protected void initChannel(SocketChannel socketChannel) throws Exception {
                    ByteBuf buffer = Unpooled.copiedBuffer("$_".getBytes());
                    socketChannel.pipeline().addLast(new DelimiterBasedFrameDecoder(1024,buffer));
                    socketChannel.pipeline().addLast(new StringDecoder());
                    socketChannel.pipeline().addLast(new Server1Handler());
                }
            });
            ChannelFuture f = sbt.bind(port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            eventLoopGroup.shutdownGracefully();
            eventLoopGroup1.shutdownGracefully();
        }
    }
}

 

Server1Handler类

package stickorApartPackageResolve.two;

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

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolve.two
 * @ClassName: Server1Handler
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/14 9:10
 * @Version: 1.0
 */
public class Server1Handler extends ChannelHandlerAdapter {

    int  counter;

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg){
        String body =  (String)msg;
        System.out.println("The time server receive order : "  + body + " ; the counter is : " + ++counter);
        body = body + "$_";
        ByteBuf bf = Unpooled.copiedBuffer(body.getBytes());
        ctx.writeAndFlush(bf);
    }

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

结果：

服务端

客户端

通过对DelimiterBasedFrameDecoder的使用，我们可以自动完成以分隔符作为码流结束标识的消息的解码，

 

三、 FixedLengthFrameDecoder

FixedLengtl1FrameDecoder是固定长度解码器，它能够按照指定的长度对消息进行自动解码，开发者不需要考虑TCP的粘包／拆包问题，非常实用。下面我们通过一个应用实例对其用法进行讲解。

Server1类：

package stickorApartPackageResolve.two;

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;
import io.netty.handler.codec.FixedLengthFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolve.two
 * @ClassName: Server1
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/14 8:54
 * @Version: 1.0
 */
public class Server1 {
    public static void main(String[] args) {
        int port = 8080;
        new Server1().bind(port);
    }

    private void bind(int port) {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        EventLoopGroup eventLoopGroup1 = new NioEventLoopGroup();

        try {
            ServerBootstrap sbt = new ServerBootstrap();
            sbt.group(eventLoopGroup,eventLoopGroup1);
            sbt.channel(NioServerSocketChannel.class);
            sbt.option(ChannelOption.SO_BACKLOG, 1024);
            sbt.childHandler(new ChannelInitializer() {
                @Override
                protected void initChannel(SocketChannel socketChannel) throws Exception {
                    //会按照这里给定的长度对消息进行截取
                    socketChannel.pipeline().addLast(new FixedLengthFrameDecoder(12));
                    socketChannel.pipeline().addLast(new StringDecoder());
                    socketChannel.pipeline().addLast(new Server1Handler());
                }
            });
            ChannelFuture f = sbt.bind(port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            eventLoopGroup.shutdownGracefully();
            eventLoopGroup1.shutdownGracefully();
        }
    }
}

Server1Handler类：

package stickorApartPackageResolve.two;

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

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolve.two
 * @ClassName: Server1Handler
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/14 9:10
 * @Version: 1.0
 */
public class Server1Handler extends ChannelHandlerAdapter {

    int  counter;

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg){
        String body =  (String)msg;
        System.out.println("The time server receive order : "  + body + " ; the counter is : " + ++counter);
        ByteBuf bf = Unpooled.copiedBuffer(body.getBytes());
        ctx.writeAndFlush(bf);
    }

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

Client1类：

package stickorApartPackageResolve.two;

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.FixedLengthFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolve.two
 * @ClassName: Client1
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/14 9:18
 * @Version: 1.0
 */
public class Client1 {

    public static void main(String[] args) {

        int port = 8080;
        String host = "127.0.0.1";
        new Client1().connect(host,port);

    }

    private void connect(String host, int port) {

        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();

        try {
            Bootstrap bs = new Bootstrap();
            bs.group(eventLoopGroup);
            bs.channel(NioSocketChannel.class);
            bs.option(ChannelOption.TCP_NODELAY, true);
            bs.handler(new ChannelInitializer() {
                @Override
                protected void initChannel(SocketChannel socketChannel) throws Exception {
                    socketChannel.pipeline().addLast(new FixedLengthFrameDecoder(12));
                    socketChannel.pipeline().addLast(new StringDecoder());
                    socketChannel.pipeline().addLast(new Client1Handler());
                }
            });
            ChannelFuture f = bs.connect(host,port).sync();
            f.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            eventLoopGroup.shutdownGracefully();
        }
    }
}

Client1Handler类：

package stickorApartPackageResolve.two;

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;

/**
 * @ProjectName: nettyTes
 * @Package: stickorApartPackageResolve.two
 * @ClassName: Client1Handler
 * @Author: Administrator
 * @Description: ${description}
 * @Date: 2019/10/14 14:35
 * @Version: 1.0
 */
public class Client1Handler extends ChannelHandlerAdapter {

    private int counter;
    private String req = "Hi!xiaoming!";

    @Override
    public void channelActive(ChannelHandlerContext ctx){
        for(int i=0; i<10; i++){
            ctx.writeAndFlush(Unpooled.copiedBuffer(req.getBytes()));
        }
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg){
        String body = (String) msg;
        System.out.println("this is : " + ++counter + "time recive " + body);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // 释放资源
        ctx.close();
    }
}

结果：

服务端

客户端：

利用FixedLengthFrameDecoder解码器，无论一次接收到多少数据报，它都会按照构造函数中设置的固定长度进行解码，如果是半包消息，FixedLengthFrameDecoder会缓存半包消息并等待下个包到达后进行拼包，直到读取到一个完整的包。