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20-Netty TCP 粘包和拆包及解决方案

發(fā)布時(shí)間：2024/3/13 编程问答 38 豆豆

生活随笔收集整理的這篇文章主要介紹了 20-Netty TCP 粘包和拆包及解决方案小編覺得挺不錯(cuò)的,現(xiàn)在分享給大家,幫大家做個(gè)參考.

TCP粘包和拆包的基本介紹

TCP是面向連接的, 面向流的, 提供可靠性服務(wù), 收發(fā)兩端(客戶端和服務(wù)器端) 都有一一成對(duì)的Socket,因此發(fā)送端為了將多個(gè)發(fā)給接收端的包, 更有效的發(fā)給對(duì)方, 使用了優(yōu)化算法(Nagle算法),將多次間隔較小且數(shù)據(jù)量小的數(shù)據(jù),合并成一個(gè)大的數(shù)據(jù)塊,然后進(jìn)行封包, 這樣做雖然提高了效率,但是接收端就難于分辨出完整的數(shù)據(jù)包了,因?yàn)槊嫦蛄鞯耐ㄐ攀菬o消息保護(hù)邊界的

由于TCP無消息保護(hù)邊界, 需要在接收端處理消息邊界問題, 也就是我們所說的粘包,拆包問題,看一張圖

示意圖TCP粘包,拆包圖解

對(duì)圖的說明

假設(shè)客戶端分別發(fā)送了兩個(gè)數(shù)據(jù)包D1和D2給服務(wù)端, 由于服務(wù)端一次讀取到字節(jié)數(shù)是不確定的,故有可能存在以下四種情況

服務(wù)端分別兩次讀取到了兩個(gè)獨(dú)立的數(shù)據(jù)包, 分別是D1 和 D2, 沒有粘包和拆包

服務(wù)端一次接收到了兩個(gè)數(shù)據(jù)包D1和D2粘在了一起,稱之為TCP粘包

服務(wù)端分兩次讀取到了數(shù)據(jù)包, 第一次讀取到了完整的D1包和D2包的部分內(nèi)容, 第二次讀取到了D2包的剩余部分, 稱之為TCP拆包

服務(wù)器分兩次讀取到了數(shù)據(jù)包, 第一次讀取到了D1包的部分內(nèi)容D1_1, 第二次讀取到了D1包的剩余部分D1_2, 和完整的D2包

TCP粘包和拆包現(xiàn)象實(shí)例

在編寫Netty程序時(shí), 如果沒有做處理,就會(huì)發(fā)生粘包和拆包問題

看一個(gè)具體的實(shí)例

NettyServer

package com.dance.netty.netty.tcp;import io.netty.bootstrap.ServerBootstrap; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.*; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioServerSocketChannel;import java.nio.charset.StandardCharsets; import java.util.UUID;public class NettyServer {public static void main(String[] args) {NioEventLoopGroup bossGroup = new NioEventLoopGroup(1);NioEventLoopGroup workerGroup = new NioEventLoopGroup();try {ServerBootstrap serverBootstrap = new ServerBootstrap();serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 128).childOption(ChannelOption.SO_KEEPALIVE, true).childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();pipeline.addLast(new NettyServerHandler());}});ChannelFuture sync = serverBootstrap.bind("127.0.0.1", 7000).sync();System.out.println("server is ready ......");sync.channel().closeFuture().sync();} catch (Exception e) {e.printStackTrace();} finally {bossGroup.shutdownGracefully();workerGroup.shutdownGracefully();}}static class NettyServerHandler extends SimpleChannelInboundHandler<ByteBuf> {private int count = 0;@Overrideprotected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {byte[] bytes = new byte[msg.readableBytes()];msg.readBytes(bytes);count++;System.out.println("服務(wù)器第"+count+"次接收到來自客戶端的數(shù)據(jù):" + new String(bytes, StandardCharsets.UTF_8));// 服務(wù)器回送數(shù)據(jù)給客戶端回送隨機(jī)的UUID給客戶端ctx.writeAndFlush(Unpooled.copiedBuffer(UUID.randomUUID().toString(),StandardCharsets.UTF_8));}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {ctx.close();cause.printStackTrace();}}}

NettyClient

package com.dance.netty.netty.tcp;import io.netty.bootstrap.Bootstrap; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.*; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioSocketChannel;import java.nio.charset.StandardCharsets;public class NettyClient {public static void main(String[] args) {NioEventLoopGroup eventExecutors = new NioEventLoopGroup();try {Bootstrap bootstrap = new Bootstrap();bootstrap.group(eventExecutors).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();pipeline.addLast(new NettyClientHandler());}});ChannelFuture sync = bootstrap.connect("127.0.0.1", 7000).sync();sync.channel().closeFuture().sync();} catch (Exception e) {e.printStackTrace();} finally {eventExecutors.shutdownGracefully();}}static class NettyClientHandler extends SimpleChannelInboundHandler<ByteBuf> {private int count = 0;@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {// 連續(xù)發(fā)送10條數(shù)據(jù)for (int i = 0; i < 10; i++) {ctx.writeAndFlush(Unpooled.copiedBuffer("hello,server!" + i, StandardCharsets.UTF_8));}}@Overrideprotected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {byte[] bytes = new byte[msg.readableBytes()];msg.readBytes(bytes);// 接收服務(wù)器的返回count++;System.out.println("客戶端第"+count+"次接收服務(wù)端的回送:" + new String(bytes, StandardCharsets.UTF_8));}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {ctx.close();cause.printStackTrace();}} }

執(zhí)行結(jié)果

Server

Client1

客戶端第1次接收服務(wù)端的回送:84653e99-0e7f-431d-a897-c215af959a3b

Client2

客戶端第1次接收服務(wù)端的回送:6f3b0e79-2f40-4066-bb6b-80f988ecec116b6bbd94-b345-46d6-8d36-a114534331a850628e04-ece1-4f58-b684-d30189f6cf26b2139027-6bda-4d40-9238-9fc0e59bc7a64b568ffe-f616-4f48-8f1c-05ecf3e817ee

分析:

服務(wù)器啟動(dòng)后到server is ready ......

第一個(gè)客戶端啟動(dòng)后 TCP將10次發(fā)送直接封包成一次直接發(fā)送,所以導(dǎo)致了服務(wù)器一次就收到了所有的數(shù)據(jù),產(chǎn)生了TCP粘包,拆包的問題

第二客戶端啟動(dòng)后 TCP將10次發(fā)送分別封裝成了5次請(qǐng)求,產(chǎn)生粘包,拆包問題

TCP粘包和拆包解決方案

使用自定義協(xié)議 + 編解碼器來解決

關(guān)鍵就是要解決服務(wù)器每次讀取數(shù)據(jù)長(zhǎng)度的問題, 這個(gè)問題解決, 就不會(huì)出現(xiàn)服務(wù)器多讀或少讀數(shù)據(jù)的問題,從而避免TCP粘包和拆包

TCP粘包, 拆包解決方案實(shí)現(xiàn)

要求客戶端發(fā)送5個(gè)Message對(duì)象, 客戶端每次發(fā)送一個(gè)Message對(duì)象

服務(wù)器端每次接收一個(gè)Message, 分5次進(jìn)行解碼, 每讀到一個(gè)Message, 會(huì)回復(fù)一個(gè)Message對(duì)象給客戶端

新建協(xié)議MessageProtocol

package com.dance.netty.netty.protocoltcp;/*** 消息協(xié)議*/ public class MessageProtocol {private int length;private byte[] content;public MessageProtocol() {}public MessageProtocol(int length, byte[] content) {this.length = length;this.content = content;}public int getLength() {return length;}public void setLength(int length) {this.length = length;}public byte[] getContent() {return content;}public void setContent(byte[] content) {this.content = content;} }

新建編碼器

package com.dance.netty.netty.protocoltcp;import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.MessageToByteEncoder;/*** 自定義協(xié)議編碼器*/ public class MyMessageProtocolEncoder extends MessageToByteEncoder<MessageProtocol> {@Overrideprotected void encode(ChannelHandlerContext ctx, MessageProtocol msg, ByteBuf out) throws Exception { // System.out.println("自定義協(xié)議---->開始編碼");// 開始發(fā)送數(shù)據(jù)out.writeInt(msg.getLength()); // 優(yōu)先發(fā)送長(zhǎng)度,定義邊界out.writeBytes(msg.getContent()); // System.out.println("自定義協(xié)議---->編碼完成");} }

新建解碼器

package com.dance.netty.netty.protocoltcp;import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.ByteToMessageDecoder;import java.util.List;public class MyMessageProtocolDecoder extends ByteToMessageDecoder {@Overrideprotected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception { // System.out.println("自定義協(xié)議---->開始解碼");// 獲取定義的邊界長(zhǎng)度int length = in.readInt();if(in.readableBytes() >= length){// 根據(jù)長(zhǎng)度讀取數(shù)據(jù)byte[] bytes = new byte[length];in.readBytes(bytes);// 反構(gòu)造成MessageProtocolMessageProtocol messageProtocol = new MessageProtocol(length, bytes);out.add(messageProtocol); // System.out.println("自定義協(xié)議---->解碼完成");}else{// 內(nèi)容長(zhǎng)度不夠}} }

新建服務(wù)器端

package com.dance.netty.netty.protocoltcp;import io.netty.bootstrap.ServerBootstrap; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.*; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioServerSocketChannel;import java.nio.charset.StandardCharsets; import java.util.UUID;public class NettyServer {public static void main(String[] args) {NioEventLoopGroup bossGroup = new NioEventLoopGroup(1);NioEventLoopGroup workerGroup = new NioEventLoopGroup();try {ServerBootstrap serverBootstrap = new ServerBootstrap();serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 128).childOption(ChannelOption.SO_KEEPALIVE, true).childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();// 加入自定義協(xié)議編解碼器pipeline.addLast(new MyMessageProtocolDecoder());pipeline.addLast(new MyMessageProtocolEncoder());pipeline.addLast(new NettyServerHandler());}});ChannelFuture sync = serverBootstrap.bind("127.0.0.1", 7000).sync();System.out.println("server is ready ......");sync.channel().closeFuture().sync();} catch (Exception e) {e.printStackTrace();} finally {bossGroup.shutdownGracefully();workerGroup.shutdownGracefully();}}static class NettyServerHandler extends SimpleChannelInboundHandler<MessageProtocol> {private int count = 0;@Overrideprotected void channelRead0(ChannelHandlerContext ctx, MessageProtocol msg) throws Exception {byte[] bytes = msg.getContent();count++;System.out.println("服務(wù)器第"+count+"次接收到來自客戶端的數(shù)據(jù):" + new String(bytes, StandardCharsets.UTF_8));// 服務(wù)器回送數(shù)據(jù)給客戶端回送隨機(jī)的UUID給客戶端byte[] s = UUID.randomUUID().toString().getBytes(StandardCharsets.UTF_8);ctx.writeAndFlush(new MessageProtocol(s.length,s));}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {ctx.close();cause.printStackTrace();}}}

新建客戶端

package com.dance.netty.netty.protocoltcp;import io.netty.bootstrap.Bootstrap; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.*; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioSocketChannel;import java.nio.charset.StandardCharsets;public class NettyClient {public static void main(String[] args) {NioEventLoopGroup eventExecutors = new NioEventLoopGroup();try {Bootstrap bootstrap = new Bootstrap();bootstrap.group(eventExecutors).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();// 加入自定義分割符號(hào) // ByteBuf delimiter = Unpooled.copiedBuffer("\r\n".getBytes()); // pipeline.addFirst(new DelimiterBasedFrameDecoder(8192, delimiter));// 添加自定義協(xié)議編解碼器pipeline.addLast(new MyMessageProtocolDecoder());pipeline.addLast(new MyMessageProtocolEncoder());pipeline.addLast(new NettyClientHandler());}});ChannelFuture sync = bootstrap.connect("127.0.0.1", 7000).sync();sync.channel().closeFuture().sync();} catch (Exception e) {e.printStackTrace();} finally {eventExecutors.shutdownGracefully();}}static class NettyClientHandler extends SimpleChannelInboundHandler<MessageProtocol> {private int count = 0;@Overridepublic void channelActive(ChannelHandlerContext ctx) throws Exception {// 連續(xù)發(fā)送10條數(shù)據(jù)for (int i = 0; i < 10; i++) {String msg = "今天天氣冷, 打火鍋" + i;byte[] bytes = msg.getBytes(StandardCharsets.UTF_8);// 使用自定義協(xié)議MessageProtocol messageProtocol = new MessageProtocol(bytes.length, bytes);ctx.writeAndFlush(messageProtocol);}}@Overrideprotected void channelRead0(ChannelHandlerContext ctx, MessageProtocol msg) throws Exception {byte[] bytes = msg.getContent();// 接收服務(wù)器的返回count++;System.out.println("客戶端第"+count+"次接收服務(wù)端的回送:" + new String(bytes, StandardCharsets.UTF_8));}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {ctx.close();cause.printStackTrace();}} }

測(cè)試

發(fā)送10次

服務(wù)器端

客戶端

ok,沒有問題, 但是真的沒有問題嗎?答案是有問題

FAQ

發(fā)送1000次

修改客戶端發(fā)送消息數(shù)量

@Override public void channelActive(ChannelHandlerContext ctx) throws Exception {// 連續(xù)發(fā)送10條數(shù)據(jù)for (int i = 0; i < 1000; i++) {......} }

重新測(cè)試

服務(wù)器端

log4j:WARN No appenders could be found for logger (io.netty.util.internal.logging.InternalLoggerFactory). log4j:WARN Please initialize the log4j system properly. log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info. server is ready ...... 服務(wù)器第1次接收到來自客戶端的數(shù)據(jù):今天天氣冷, 打火鍋0 ...... 服務(wù)器第31次接收到來自客戶端的數(shù)據(jù):今天天氣冷, 打火鍋30 服務(wù)器第32次接收到來自客戶端的數(shù)據(jù):今天天氣冷, 打火鍋31 io.netty.handler.codec.DecoderException: java.lang.NegativeArraySizeExceptionat io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:459)at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:265)at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1412)at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:943)at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:141)at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:645)at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:580)at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:497)at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:459)at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:886)at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)at java.lang.Thread.run(Thread.java:748) Caused by: java.lang.NegativeArraySizeExceptionat com.dance.netty.netty.protocoltcp.MyMessageProtocolDecoder.decode(MyMessageProtocolDecoder.java:17)at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:489)at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:428)... 16 more io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerIndex(1022) + length(4) exceeds writerIndex(1024): PooledUnsafeDirectByteBuf(ridx: 1022, widx: 1024, cap: 1024)at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:459)at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:392)at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:359)at io.netty.handler.codec.ByteToMessageDecoder.channelInactive(ByteToMessageDecoder.java:342)at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245)at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231)at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:224)at io.netty.channel.DefaultChannelPipeline$HeadContext.channelInactive(DefaultChannelPipeline.java:1407)at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245)at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231)at io.netty.channel.DefaultChannelPipeline.fireChannelInactive(DefaultChannelPipeline.java:925)at io.netty.channel.AbstractChannel$AbstractUnsafe$8.run(AbstractChannel.java:822)at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404)at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:463)at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:886)at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)at java.lang.Thread.run(Thread.java:748) Caused by: java.lang.IndexOutOfBoundsException: readerIndex(1022) + length(4) exceeds writerIndex(1024): PooledUnsafeDirectByteBuf(ridx: 1022, widx: 1024, cap: 1024)at io.netty.buffer.AbstractByteBuf.checkReadableBytes0(AbstractByteBuf.java:1403)at io.netty.buffer.AbstractByteBuf.readInt(AbstractByteBuf.java:786)at com.dance.netty.netty.protocoltcp.MyMessageProtocolDecoder.decode(MyMessageProtocolDecoder.java:14)at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:489)at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:428)... 17 more

what ? 直接報(bào)錯(cuò)了, 數(shù)組下標(biāo)越界, 讀索引1022 + 長(zhǎng)度4 > 寫縮影1024了

這個(gè)是什么問題呢 ? 我看網(wǎng)上關(guān)于這個(gè)BUG的解決方案很少,基本沒有, 好多都是貼問題的, 我翻了將近1個(gè)小時(shí),才找到一個(gè)大佬寫的一篇文章解決了, 感謝大佬

博客地址:

https://blog.csdn.net/u011035407/article/details/80454511

問題描述:

這樣在剛開始的工作中數(shù)據(jù)包傳輸沒有問題，不過數(shù)據(jù)包的大小超過512b的時(shí)候就會(huì)拋出異常了。

解決方案

配合解碼器DelimiterBasedFrameDecoder一起使用，在數(shù)據(jù)包的末尾使用換行符\n表示本次數(shù)據(jù)包已經(jīng)結(jié)束，當(dāng)DelimiterBasedFrameDecoder把數(shù)據(jù)切割之后，再使用ByteToMessageDecoder實(shí)現(xiàn)decode方法把數(shù)據(jù)流轉(zhuǎn)換為Message對(duì)象。

我們?cè)?span id="ze8trgl8bvbq" class="ne-text">ChannelPipeline加入DelimiterBasedFrameDecoder解碼器

客戶端和服務(wù)器端都加

//使用\n作為分隔符 pipeline.addLast(new LoggingHandler(LogLevel.INFO)); pipeline.addLast(new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()));

在MessageToByteEncoder的實(shí)現(xiàn)方法encode()增加out.writeBytes(new byte[]{'\n'});

//在寫出字節(jié)流的末尾增加\n表示數(shù)據(jù)結(jié)束 out.writeBytes(new byte[]{'\n'});

這時(shí)候就可以愉快的繼續(xù)處理數(shù)據(jù)了。等我還沒有高興半天的時(shí)候，問題又來了。還是一樣的問題

等等等，，，怎么又報(bào)錯(cuò)了，不是已經(jīng)加了黏包處理了嗎？？，解決問題把，首先看解析的數(shù)據(jù)包結(jié)構(gòu)

+-------------------------------------------------+| 0 1 2 3 4 5 6 7 8 9 a b c d e f | +--------+-------------------------------------------------+----------------+ |00000000| 01 01 01 00 00 00 06 00 00 01 0a 7b 22 69 64 22 |...........{"id"| |00000010| 3a 33 2c 22 75 73 65 72 6e 61 6d 65 22 3a 22 31 |:3,"username":"1| |00000020| 38 35 30 30 33 34 30 31 36 39 22 2c 22 6e 69 63 |8500340169","nic| |00000030| 6b 6e 61 6d 65 22 3a 22 e4 bb 96 e5 9b 9b e5 a4 |kname":"........| |00000040| a7 e7 88 b7 22 2c 22 72 6f 6f 6d 49 64 22 3a 31 |....","roomId":1| |00000050| 35 32 37 32 33 38 35 36 39 34 37 34 2c 22 74 65 |527238569474,"te| |00000060| 61 6d 4e 61 6d 65 22 3a 22 e4 bf 84 e7 bd 97 e6 |amName":".......| |00000070| 96 af 22 2c 22 75 6e 69 74 73 22 3a 7b 22 75 6e |..","units":{"un| |00000080| 69 74 31 22 3a 7b 22 78 22 3a 31 30 2e 30 2c 22 |it1":{"x":10.0,"| |00000090| 79 22 3a 31 30 2e 30 7d 2c 22 75 6e 69 74 32 22 |y":10.0},"unit2"| |000000a0| 3a 7b 22 78 22 3a 31 30 2e 30 2c 22 79 22 3a 31 |:{"x":10.0,"y":1| |000000b0| 30 2e 30 7d 2c 22 75 6e 69 74 33 22 3a 7b 22 78 |0.0},"unit3":{"x| |000000c0| 22 3a 31 30 2e 30 2c 22 79 22 3a 31 30 2e 30 7d |":10.0,"y":10.0}| |000000d0| 2c 22 75 6e 69 74 34 22 3a 7b 22 78 22 3a 31 30 |,"unit4":{"x":10| |000000e0| 2e 30 2c 22 79 22 3a 31 30 2e 30 7d 2c 22 75 6e |.0,"y":10.0},"un| |000000f0| 69 74 35 22 3a 7b 22 78 22 3a 31 30 2e 30 2c 22 |it5":{"x":10.0,"| |00000100| 79 22 3a 31 30 2e 30 7d 7d 2c 22 73 74 61 74 75 |y":10.0}},"statu| |00000110| 73 22 3a 31 7d 0a |s":1}. | +--------+-------------------------------------------------+----------------+

接收到的數(shù)據(jù)是完整的沒錯(cuò)，但是還是報(bào)錯(cuò)了，而且數(shù)據(jù)結(jié)尾的字節(jié)的確是0a，轉(zhuǎn)化成字符就是\n沒有問題啊。

在ByteToMessageDecoder的decode方法里打印ByteBuf buf的長(zhǎng)度之后，問題找到了長(zhǎng)度 : 10

這就是說在進(jìn)入到ByteToMessageDecoder這個(gè)解碼器的時(shí)候，數(shù)據(jù)包已經(jīng)只剩下10個(gè)長(zhǎng)度了，那么長(zhǎng)的數(shù)據(jù)被上個(gè)解碼器DelimiterBasedFrameDecoder隔空劈開了- -。問題出現(xiàn)在哪呢，看上面那塊字節(jié)流的字節(jié)，找到第11個(gè)字節(jié)，是0a。。。。因?yàn)椴皇菢?biāo)準(zhǔn)的json格式，最前面使用了3個(gè)字節(jié) 加上2個(gè)int長(zhǎng)度的屬性，所以數(shù)據(jù)包頭應(yīng)該是11個(gè)字節(jié)長(zhǎng)。

而DelimiterBasedFrameDecoder在讀到第11個(gè)字節(jié)的時(shí)候讀成了\n，自然而然的就認(rèn)為這個(gè)數(shù)據(jù)包已經(jīng)結(jié)束了，而數(shù)據(jù)進(jìn)入到ByteToMessageDecoder的時(shí)候就會(huì)因?yàn)橐?guī)定的body長(zhǎng)度不等于length長(zhǎng)度而出現(xiàn)問題。

思來想去不實(shí)用\n 這樣的單字節(jié)作為換行符，很容易在數(shù)據(jù)流中遇到，轉(zhuǎn)而使用\r\n倆字節(jié)來處理，而這倆字節(jié)出現(xiàn)在前面兩個(gè)int長(zhǎng)度中的幾率應(yīng)該很小。

最終解決

在客戶端和服務(wù)器端的pipeline中添加以 "\r\n" 定義為邊界的符號(hào)來標(biāo)識(shí)數(shù)據(jù)包結(jié)束

//這里使用自定義分隔符 ByteBuf delimiter = Unpooled.copiedBuffer("\r\n".getBytes()); pipeline.addFirst(new DelimiterBasedFrameDecoder(8192, delimiter));

Server端

Client端

編碼器中發(fā)送結(jié)束位置增加

//這里最后修改使用\r\n out.writeBytes(new byte[]{'\r','\n'});

再次運(yùn)行程序數(shù)據(jù)包可以正常接收了。

最終測(cè)試

服務(wù)器端

客戶端

總結(jié)

以前使用netty的時(shí)候也僅限于和硬件交互，而當(dāng)時(shí)的硬件受限于成本問題是一條一條處理數(shù)據(jù)包的，所以基本上不會(huì)考慮黏包問題

然后就是ByteToMessageDecoder和MessageToByteEncoder兩個(gè)類是比較底層實(shí)現(xiàn)數(shù)據(jù)流處理的，并沒有帶有拆包黏包的處理機(jī)制，需要自己在數(shù)據(jù)包頭規(guī)定包的長(zhǎng)度，而且無法處理過大的數(shù)據(jù)包，因?yàn)槲乙婚_始首先使用了這種方式處理數(shù)據(jù)，所以后來就沒有再換成DelimiterBasedFrameDecoder加 StringDecoder來解析數(shù)據(jù)包，最后使用json直接轉(zhuǎn)化為對(duì)象。

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