Netty提供的TCP数据拆包、粘包解决方案

1.前言

关于TCP的数据拆包、粘包的介绍,我在上一篇文章里面已经有过介绍。

想要了解一下的,请点击这里 Chick Here!

今天我们要讲解的是Netty提供的两种解决方案:

  1. DelimiterBasedFrameDecoder
  2. FixedLengthFrameDecoder

2.关于Decoder

  1. 先观察下两段代码的不同

    (1)使用StringDecoder之前

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { try { ByteBuf in = (ByteBuf) msg;
    String str = in.toString(CharsetUtil.UTF_8);
    System.out.println("Client:"+str); } finally {
    ReferenceCountUtil.release(msg);
    }
    }

    (2)使用StringDecoder之后

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { try {
    String str = (String) msg;
    System.out.println("Client:"+str); } finally {
    ReferenceCountUtil.release(msg);
    }
    }
  2. 关于Decoder

    decoder:n. 解码器

    在我看来,Netty数据的解析方式大概为:

    发送过程:Buffer------>数据报------>比特流

    接受过程:Buffer<------数据报<------比特流

    所以我们接受到的msg是一个ButeBuf

    使用了Decoder(这里使用StringDecoder举例)之后:

    发送过程:Buffer------>数据报------>比特流

    接受过程:String<------Buffer<------数据报<------比特流

    相当于ByteBuf按照StringDecoder的解码规则,把msg翻译成为了一个字符串。

  3. 如何使用Decoder

    (1)实际代码演示:

    package com.xm.netty.demo02;
    
    import java.net.InetSocketAddress;
    
    import io.netty.bootstrap.ServerBootstrap;
    import io.netty.channel.Channel;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.ChannelInitializer;
    import io.netty.channel.EventLoopGroup;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.nio.NioServerSocketChannel;
    import io.netty.handler.codec.string.StringDecoder; public class Server { private final int port; public Server(int port) {
    this.port = port;
    } public static void main(String[] args) { int port = 8989;
    try {
    new Server(port).start();
    } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    } } private void start() throws InterruptedException {
    EventLoopGroup g1 = new NioEventLoopGroup();
    EventLoopGroup g2 = new NioEventLoopGroup();
    try {
    ServerBootstrap bootstrap = new ServerBootstrap();
    bootstrap
    .group(g1,g2)
    .channel(NioServerSocketChannel.class)
    .localAddress(new InetSocketAddress( port))
    .childHandler(new ChannelInitializer() {
    @Override
    protected void initChannel(Channel ch) throws Exception {
    ch.pipeline().addLast(new StringDecoder());
    ch.pipeline().addLast(new ServerHandler());
    }
    });
    ChannelFuture future = bootstrap.bind().sync();
    future.channel().closeFuture().sync();
    } finally {
    g1.shutdownGracefully().sync();
    g2.shutdownGracefully().sync();
    }
    } }

    代码改动:

    ch.pipeline().addLast(new StringDecoder());

    ​ ch.pipeline().addLast(new ServerHandler());

    (2)多个Decoder的使用顺序:

    从前往后,依次解码

    假设我们有个通过字符串变化为时间的TimeDecoder:

    ch.pipeline().addLast(new StringDecoder());

    ch.pipeline().addLast(new TimeDecoder());

    ​ ch.pipeline().addLast(new ServerHandler());

    解析规则为:

3.DelimiterBasedFrameDecoder

  1. 关于DelimiterBasedFrameDecoder

    其实很简单,就是在一个缓冲区的末尾添加一个结束字符。

    在规定了最大长度的缓冲区里,遇到一个特殊字符,就截取一次。

    原理类似于String的split()方法。

  2. 代码实现

    (1)服务端Server

    package com.xm.netty.demo03;
    
    import java.net.InetSocketAddress;
    
    import io.netty.bootstrap.ServerBootstrap;
    import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.Channel;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.ChannelInitializer;
    import io.netty.channel.EventLoopGroup;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.nio.NioServerSocketChannel;
    import io.netty.handler.codec.DelimiterBasedFrameDecoder;
    import io.netty.handler.codec.string.StringDecoder; public class Server { private final int port; public Server(int port) {
    this.port = port;
    } public static void main(String[] args) { int port = 8989;
    try {
    new Server(port).start();
    } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    } } private void start() throws InterruptedException {
    EventLoopGroup g1 = new NioEventLoopGroup();
    EventLoopGroup g2 = new NioEventLoopGroup();
    try {
    ServerBootstrap bootstrap = new ServerBootstrap();
    bootstrap
    .group(g1,g2)
    .channel(NioServerSocketChannel.class)
    .localAddress(new InetSocketAddress( port))
    .childHandler(new ChannelInitializer() {
    @Override
    protected void initChannel(Channel ch) throws Exception {
    ByteBuf buf = Unpooled.copiedBuffer("$".getBytes());
    ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024,buf));
    ch.pipeline().addLast(new StringDecoder());
    ch.pipeline().addLast(new ServerHandler());
    }
    });
    ChannelFuture future = bootstrap.bind().sync();
    future.channel().closeFuture().sync();
    } finally {
    g1.shutdownGracefully().sync();
    g2.shutdownGracefully().sync();
    }
    } }

    (2)服务端ServerHandler

    package com.xm.netty.demo03;
    
    import java.time.LocalDateTime;
    import java.time.format.DateTimeFormatter; import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.ChannelHandlerAdapter;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.util.CharsetUtil; public class ServerHandler extends ChannelHandlerAdapter { @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { String str = (String) msg;
    System.out.println("Server:"+str);
    str = "服务器返回--->"+ str+"$";
    ctx.writeAndFlush(Unpooled.copiedBuffer(str.getBytes()));
    } @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    cause.printStackTrace();
    ctx.close();
    } @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"一个客户端连接上服务器!");
    } }

    (3)客户端Client

    package com.xm.netty.demo03;
    
    import java.time.LocalDateTime;
    import java.time.format.DateTimeFormatter; 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.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; public class Client { private final int port;
    private final String host; public Client(int port, String host) {
    this.port = port;
    this.host = host;
    } public static void main(String[] args) {
    String host = "127.0.0.1";
    int port = 8989;
    try {
    new Client(port, host).start();
    } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    }
    } private void start() throws InterruptedException { EventLoopGroup group = new NioEventLoopGroup();
    try {
    Bootstrap bootstrap = new Bootstrap();
    bootstrap
    .group(group)
    .channel(NioSocketChannel.class)
    .remoteAddress(host, port)
    .handler(new ChannelInitializer<SocketChannel>() { @Override
    protected void initChannel(SocketChannel ch) throws Exception {
    ByteBuf buf = Unpooled.copiedBuffer("$".getBytes());
    ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024,buf));
    ch.pipeline().addLast(new StringDecoder());
    ch.pipeline().addLast(new ClientHandler());
    } }); ChannelFuture future = bootstrap.connect().sync(); for(int i=10;i<20;i++) {
    String str = DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now()) + "---- " +i+"<<<$";
    future.channel().write(Unpooled.copiedBuffer(str.getBytes()));
    } future.channel().flush(); //future.channel().writeAndFlush(Unpooled.copiedBuffer("Hello Netty!".getBytes())); future.channel().closeFuture().sync();
    } finally {
    group.shutdownGracefully().sync();
    } } }

    (4)客户端ClientHandler

    package com.xm.netty.demo03;
    
    import java.time.LocalDateTime;
    import java.time.format.DateTimeFormatter; import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.ChannelHandlerAdapter;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.util.CharsetUtil;
    import io.netty.util.ReferenceCountUtil; public class ClientHandler extends ChannelHandlerAdapter { @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { try {
    String str = (String) msg;
    System.out.println("Client:"+str); } finally {
    ReferenceCountUtil.release(msg);
    }
    } @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    cause.printStackTrace();
    ctx.close();
    } @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"已连接服务器!");
    } }
  3. 运行结果截图

    (1)服务端运行结果:

    (2)客户端运行结果:

4.FixedLengthFrameDecoder

  1. 关于FixedLengthFrameDecoder

    其实很简单,就是对规定的发送的数据进行限制长度,

    当符合这个长度的情况下,就可以解析。

    假设你发送一个’123456‘,’654321‘

    那么解析的状况为’12345‘,’66543‘

  2. 代码实现

    (1)服务端Server

    package com.xm.netty.demo04;
    
    import java.net.InetSocketAddress;
    
    import io.netty.bootstrap.ServerBootstrap;
    import io.netty.channel.Channel;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.ChannelInitializer;
    import io.netty.channel.EventLoopGroup;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.nio.NioServerSocketChannel;
    import io.netty.handler.codec.FixedLengthFrameDecoder;
    import io.netty.handler.codec.string.StringDecoder; public class Server { private final int port; public Server(int port) {
    this.port = port;
    } public static void main(String[] args) { int port = 8989;
    try {
    new Server(port).start();
    } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    } } private void start() throws InterruptedException {
    EventLoopGroup g1 = new NioEventLoopGroup();
    EventLoopGroup g2 = new NioEventLoopGroup();
    try {
    ServerBootstrap bootstrap = new ServerBootstrap();
    bootstrap
    .group(g1,g2)
    .channel(NioServerSocketChannel.class)
    .localAddress(new InetSocketAddress( port))
    .childHandler(new ChannelInitializer() {
    @Override
    protected void initChannel(Channel ch) throws Exception {
    ch.pipeline().addLast(new FixedLengthFrameDecoder(5));
    ch.pipeline().addLast(new StringDecoder());
    ch.pipeline().addLast(new ServerHandler());
    }
    });
    ChannelFuture future = bootstrap.bind().sync();
    future.channel().closeFuture().sync();
    } finally {
    g1.shutdownGracefully().sync();
    g2.shutdownGracefully().sync();
    }
    } }

    (2)服务端ServerHandler

    package com.xm.netty.demo04;
    
    import java.time.LocalDateTime;
    import java.time.format.DateTimeFormatter; import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.ChannelHandlerAdapter;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.util.CharsetUtil; public class ServerHandler extends ChannelHandlerAdapter { @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { String str = (String) msg;
    System.out.println("Server:"+str);
    ctx.writeAndFlush(Unpooled.copiedBuffer(str.getBytes()));
    } @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    cause.printStackTrace();
    ctx.close();
    } @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"一个客户端连接上服务器!");
    } }

    (3)客户端Client

    package com.xm.netty.demo04;
    
    import java.time.LocalDateTime;
    import java.time.format.DateTimeFormatter; import io.netty.bootstrap.Bootstrap;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.ChannelInitializer;
    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; public class Client { private final int port;
    private final String host; public Client(int port, String host) {
    this.port = port;
    this.host = host;
    } public static void main(String[] args) {
    String host = "127.0.0.1";
    int port = 8989;
    try {
    new Client(port, host).start();
    } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
    }
    } private void start() throws InterruptedException { EventLoopGroup group = new NioEventLoopGroup();
    try {
    Bootstrap bootstrap = new Bootstrap();
    bootstrap
    .group(group)
    .channel(NioSocketChannel.class)
    .remoteAddress(host, port)
    .handler(new ChannelInitializer<SocketChannel>() { @Override
    protected void initChannel(SocketChannel ch) throws Exception {
    ch.pipeline().addLast(new FixedLengthFrameDecoder(5));
    ch.pipeline().addLast(new StringDecoder());
    ch.pipeline().addLast(new ClientHandler());
    } }); ChannelFuture future = bootstrap.connect().sync(); for(int i=123450;i<123460;i++) {
    String str = ""+i;
    future.channel().write(Unpooled.copiedBuffer(str.getBytes()));
    }
    future.channel().flush(); //future.channel().writeAndFlush(Unpooled.copiedBuffer("Hello Netty!".getBytes())); future.channel().closeFuture().sync();
    } finally {
    group.shutdownGracefully().sync();
    } } }

    (4)客户端ClientHandler

    package com.xm.netty.demo04;
    
    import java.time.LocalDateTime;
    import java.time.format.DateTimeFormatter; import io.netty.buffer.ByteBuf;
    import io.netty.buffer.Unpooled;
    import io.netty.channel.ChannelHandlerAdapter;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.util.CharsetUtil;
    import io.netty.util.ReferenceCountUtil; public class ClientHandler extends ChannelHandlerAdapter { @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { try {
    String str = (String) msg;
    System.out.println("Client:"+str); } finally {
    ReferenceCountUtil.release(msg);
    }
    } @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    cause.printStackTrace();
    ctx.close();
    } @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
    System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"已连接服务器!");
    } }
  3. 运行结果截图

    (1)服务端运行结果:

    (2)客户端运行结果:

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