Netty解决TCP粘包/拆包问题 - 按行分隔字符串解码器
服务端
package org.zln.netty.five.timer; import io.netty.bootstrap.ServerBootstrap; import io.netty.channel.ChannelFuture; import io.netty.channel.ChannelOption; import io.netty.channel.EventLoopGroup; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.nio.NioServerSocketChannel; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * 时间服务器服务端 * Created by sherry on 16/11/5. */ public class TimerServer { /** * 服务端绑定端口号 */ private int PORT; public TimerServer(int PORT) { this.PORT = PORT; } /** * 日志 */ private static Logger logger = LoggerFactory.getLogger(TimerServer.class); public void bind() { /* NioEventLoopGroup是线程池组 包含了一组NIO线程,专门用于网络事件的处理 bossGroup:服务端,接收客户端连接 workGroup:进行SocketChannel的网络读写 */ EventLoopGroup bossGroup = new NioEventLoopGroup(); EventLoopGroup workGroup = new NioEventLoopGroup(); try { /* ServerBootstrap:用于启动NIO服务的辅助类,目的是降低服务端的开发复杂度 */ ServerBootstrap serverBootstrap = new ServerBootstrap(); serverBootstrap.group(bossGroup, workGroup) .channel(NioServerSocketChannel.class) .option(ChannelOption.SO_BACKLOG, 1024)//配置TCP参数,能够设置很多,这里就只设置了backlog=1024, .childHandler(new TimerServerInitializer());//绑定I/O事件处理类 logger.debug("绑定端口号:" + PORT + ",等待同步成功"); /* bind:绑定端口 sync:同步阻塞方法,等待绑定完成,完成后返回 ChannelFuture ,主要用于通知回调 */ ChannelFuture channelFuture = serverBootstrap.bind(PORT).sync(); logger.debug("等待服务端监听窗口关闭"); /* closeFuture().sync():为了阻塞,服务端链路关闭后才退出.也是一个同步阻塞方法 */ channelFuture.channel().closeFuture().sync(); } catch (InterruptedException e) { logger.error(e.getMessage(), e); } finally { logger.debug("优雅退出,释放线程池资源"); bossGroup.shutdownGracefully(); workGroup.shutdownGracefully(); } } }
1 package org.zln.netty.five.timer; 2 3 import io.netty.channel.ChannelInitializer; 4 import io.netty.channel.ChannelPipeline; 5 import io.netty.channel.socket.SocketChannel; 6 import io.netty.handler.codec.LineBasedFrameDecoder; 7 import io.netty.handler.codec.string.StringDecoder; 8 9 /** 10 * Created by sherry on 16/11/5. 11 */ 12 public class TimerServerInitializer extends ChannelInitializer<SocketChannel> { 13 @Override 14 protected void initChannel(SocketChannel socketChannel) throws Exception { 15 16 ChannelPipeline pipeline = socketChannel.pipeline(); 17 18 pipeline.addLast(new LineBasedFrameDecoder(1024)); 19 pipeline.addLast(new StringDecoder()); 20 pipeline.addLast(new TimerServerHandler()); 21 22 23 24 } 25 }
1 package org.zln.netty.five.timer; 2 3 import io.netty.buffer.ByteBuf; 4 import io.netty.buffer.Unpooled; 5 import io.netty.channel.ChannelHandlerAdapter; 6 import io.netty.channel.ChannelHandlerContext; 7 import org.slf4j.Logger; 8 import org.slf4j.LoggerFactory; 9 10 import java.text.SimpleDateFormat; 11 import java.util.Date; 12 13 /** 14 * Handler主要用于对网络事件进行读写操作,是真正的业务类 15 * 通常只需要关注 channelRead 和 exceptionCaught 方法 16 * Created by sherry on 16/11/5. 17 */ 18 public class TimerServerHandler extends ChannelHandlerAdapter { 19 20 /** 21 * 日志 22 */ 23 private Logger logger = LoggerFactory.getLogger(TimerServerHandler.class); 24 25 private static int count = 0; 26 27 @Override 28 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { 29 30 String body = (String) msg; 31 logger.debug("第 "+(++count)+" 次收到请求 - "+body); 32 33 String timeNow = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss SSS").format(new Date())+System.lineSeparator(); 34 35 //获取发送给客户端的数据 36 ByteBuf resBuf = Unpooled.copiedBuffer(timeNow.getBytes("UTF-8")); 37 38 ctx.writeAndFlush(resBuf); 39 } 40 41 42 @Override 43 public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { 44 //将消息发送队列中的消息写入到SocketChannel中发送给对方 45 logger.debug("channelReadComplete"); 46 ctx.flush(); 47 } 48 49 @Override 50 public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { 51 //发生异常时,关闭 ChannelHandlerContext,释放ChannelHandlerContext 相关的句柄等资源 52 logger.error(cause.getMessage(),cause); 53 ctx.close(); 54 } 55 }
客户端
1 package org.zln.netty.five.timer; 2 3 import io.netty.bootstrap.Bootstrap; 4 import io.netty.channel.ChannelFuture; 5 import io.netty.channel.ChannelOption; 6 import io.netty.channel.EventLoopGroup; 7 import io.netty.channel.nio.NioEventLoopGroup; 8 import io.netty.channel.socket.nio.NioSocketChannel; 9 import org.slf4j.Logger; 10 import org.slf4j.LoggerFactory; 11 12 /** 13 * 时间服务器客户端 14 * Created by sherry on 16/11/5. 15 */ 16 public class TimerClient { 17 /** 18 * 日志 19 */ 20 private Logger logger = LoggerFactory.getLogger(TimerServer.class); 21 22 private String HOST; 23 private int PORT; 24 25 public TimerClient(String HOST, int PORT) { 26 this.HOST = HOST; 27 this.PORT = PORT; 28 } 29 30 public void connect(){ 31 //配置客户端NIO线程组 32 EventLoopGroup eventLoopGroup = new NioEventLoopGroup(); 33 try { 34 Bootstrap bootstrap = new Bootstrap(); 35 bootstrap.group(eventLoopGroup) 36 .channel(NioSocketChannel.class) 37 .option(ChannelOption.TCP_NODELAY,true) 38 .handler(new TimerClientInitializer()); 39 //发起异步连接操作 40 logger.debug("发起异步连接操作 - start"); 41 ChannelFuture channelFuture = bootstrap.connect(HOST,PORT).sync(); 42 logger.debug("发起异步连接操作 - end"); 43 //等待客户端链路关闭 44 logger.debug("等待客户端链路关闭 - start"); 45 channelFuture.channel().closeFuture().sync(); 46 logger.debug("等待客户端链路关闭 - end"); 47 } catch (InterruptedException e) { 48 logger.error(e.getMessage(),e); 49 }finally { 50 //优雅的关闭 51 eventLoopGroup.shutdownGracefully(); 52 } 53 } 54 }
1 package org.zln.netty.five.timer; 2 3 import io.netty.channel.ChannelInitializer; 4 import io.netty.channel.ChannelPipeline; 5 import io.netty.channel.socket.SocketChannel; 6 import io.netty.handler.codec.LineBasedFrameDecoder; 7 import io.netty.handler.codec.string.StringDecoder; 8 9 /** 10 * Created by sherry on 16/11/5. 11 */ 12 public class TimerClientInitializer extends ChannelInitializer<SocketChannel> { 13 @Override 14 protected void initChannel(SocketChannel socketChannel) throws Exception { 15 ChannelPipeline pipeline = socketChannel.pipeline(); 16 pipeline.addLast(new LineBasedFrameDecoder(1024)); 17 pipeline.addLast(new StringDecoder()); 18 pipeline.addLast(new TimerClientHandler()); 19 } 20 }
1 package org.zln.netty.five.timer; 2 3 import io.netty.buffer.ByteBuf; 4 import io.netty.buffer.Unpooled; 5 import io.netty.channel.ChannelHandlerAdapter; 6 import io.netty.channel.ChannelHandlerContext; 7 import org.slf4j.Logger; 8 import org.slf4j.LoggerFactory; 9 10 import java.io.UnsupportedEncodingException; 11 12 /** 13 * Created by sherry on 16/11/5. 14 */ 15 public class TimerClientHandler extends ChannelHandlerAdapter { 16 17 /** 18 * 日志 19 */ 20 private Logger logger = LoggerFactory.getLogger(TimerClientHandler.class); 21 22 private static int count = 0; 23 24 @Override 25 public void channelActive(ChannelHandlerContext ctx) throws Exception { 26 logger.debug("客户端连接上了服务端"); 27 28 //发送请求 29 ByteBuf reqBuf = null; 30 for (int i = 0; i < 100; i++) { 31 reqBuf = getReq("GET TIME"+System.lineSeparator()); 32 ctx.writeAndFlush(reqBuf); 33 } 34 35 36 } 37 38 /** 39 * 将字符串包装成ByteBuf 40 * @param s 41 * @return 42 */ 43 private ByteBuf getReq(String s) throws UnsupportedEncodingException { 44 byte[] data = s.getBytes("UTF-8"); 45 ByteBuf reqBuf = Unpooled.buffer(data.length); 46 reqBuf.writeBytes(data); 47 return reqBuf; 48 } 49 50 @Override 51 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { 52 String body = (String) msg; 53 logger.debug("这是收到的第 "+(++count)+" 笔响应 -- "+body); 54 } 55 56 @Override 57 public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { 58 ctx.close(); 59 } 60 }
这里主要使用 LineBasedFrameDecoder 和 StringDecoder 来实现解决粘包问题
原理如下：
LineBasedFrameDecoder 依次遍历 ByteBuf 中的可读字节，判断是否有 \n 或 \r\n，如果有，就作为结束位置。从可读索引到结束位置区间的字节组成一行。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懈怠结束符两种解码方式。同时支持配置单行的最大长度。如果读取到了最大长度仍旧没有发现换行符，就会抛出异常，同时忽略掉之前读到的数据。
StringDecoder 的作用就是讲接收到的对象转化成字符串，然后继续调用handler。这样就不需要再handler中手动将对象转化成字符串了，直接强制转化就行。
LineBasedFrameDecoder+StringDecoder组合就是按行切割的文本解码器，用来解决TCP的粘包和拆包问题。
