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:
- DelimiterBasedFrameDecoder
- FixedLengthFrameDecoder
2.关于Decoder
-
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); } }
- 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。
- 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
- 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。
- 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!"); } }
- 运行结果截图
(1)服务端运行结果:
(2)客户端运行结果:
4.FixedLengthFrameDecoder
- 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‘
- 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!"); } }
- 运行结果截图
(1)服务端运行结果:
(2)客户端运行结果:
原文地址:https://www.cnblogs.com/TimerHotel/p/netty03.html