对图的说明
假设客户端分别发送了两个数据包D1和D2给服务端, 由于服务端一次读取到字节数是不确定的,故有可能存在以下四种情况
在编写Netty程序时, 如果没有做处理,就会发生粘包和拆包问题
看一个具体的实例
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>() {
@Override
protected 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;
@Override
protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
byte[] bytes = new byte[msg.readableBytes()];
msg.readBytes(bytes);
count++;
System.out.println("服务器第"+count+"次接收到来自客户端的数据:" + new String(bytes, StandardCharsets.UTF_8));
// 服务器回送数据给客户端 回送随机的UUID给客户端
ctx.writeAndFlush(Unpooled.copiedBuffer(UUID.randomUUID().toString(),StandardCharsets.UTF_8));
}
@Override
public 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>() {
@Override
protected 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;
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
// 连续发送10条数据
for (int i = 0; i < 10; i++) {
ctx.writeAndFlush(Unpooled.copiedBuffer("hello,server!" + i, StandardCharsets.UTF_8));
}
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws Exception {
byte[] bytes = new byte[msg.readableBytes()];
msg.readBytes(bytes);
// 接收服务器的返回
count++;
System.out.println("客户端第"+count+"次接收服务端的回送:" + new String(bytes, StandardCharsets.UTF_8));
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
cause.printStackTrace();
}
}
}
执行结果
Server
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 ......
服务器第1次接收到来自客户端的数据:hello,server!0hello,server!1hello,server!2hello,server!3hello,server!4hello,server!5hello,server!6hello,server!7hello,server!8hello,server!9
服务器第1次接收到来自客户端的数据:hello,server!0
服务器第2次接收到来自客户端的数据:hello,server!1
服务器第3次接收到来自客户端的数据:hello,server!2hello,server!3hello,server!4
服务器第4次接收到来自客户端的数据:hello,server!5hello,server!6
服务器第5次接收到来自客户端的数据:hello,server!7hello,server!8hello,server!9
Client1
客户端第1次接收服务端的回送:84653e99-0e7f-431d-a897-c215af959a3b
Client2
客户端第1次接收服务端的回送:6f3b0e79-2f40-4066-bb6b-80f988ecec116b6bbd94-b345-46d6-8d36-a114534331a850628e04-ece1-4f58-b684-d30189f6cf26b2139027-6bda-4d40-9238-9fc0e59bc7a64b568ffe-f616-4f48-8f1c-05ecf3e817ee
分析:
服务器启动后到server is ready ......
第一个客户端启动后 TCP将10次发送直接封包成一次直接发送,所以导致了服务器一次就收到了所有的数据,产生了TCP粘包,拆包的问题
第二客户端启动后 TCP将10次发送分别封装成了5次请求,产生粘包,拆包问题
package com.dance.netty.netty.protocoltcp;
/**
* 消息协议
*/
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;
}
}
package com.dance.netty.netty.protocoltcp;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
/**
* 自定义协议编码器
*/
public class MyMessageProtocolEncoder extends MessageToByteEncoder<MessageProtocol> {
@Override
protected void encode(ChannelHandlerContext ctx, MessageProtocol msg, ByteBuf out) throws Exception {
// System.out.println("自定义协议---->开始编码");
// 开始发送数据
out.writeInt(msg.getLength()); // 优先发送长度,定义边界
out.writeBytes(msg.getContent());
// System.out.println("自定义协议---->编码完成");
}
}
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 {
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
// System.out.println("自定义协议---->开始解码");
// 获取定义的边界长度
int length = in.readInt();
if(in.readableBytes() >= length){
// 根据长度读取数据
byte[] bytes = new byte[length];
in.readBytes(bytes);
// 反构造成MessageProtocol
MessageProtocol messageProtocol = new MessageProtocol(length, bytes);
out.add(messageProtocol);
// System.out.println("自定义协议---->解码完成");
}else{
// 内容长度不够
}
}
}
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>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
// 加入自定义协议编解码器
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;
@Override
protected void channelRead0(ChannelHandlerContext ctx, MessageProtocol msg) throws Exception {
byte[] bytes = msg.getContent();
count++;
System.out.println("服务器第"+count+"次接收到来自客户端的数据:" + new String(bytes, StandardCharsets.UTF_8));
// 服务器回送数据给客户端 回送随机的UUID给客户端
byte[] s = UUID.randomUUID().toString().getBytes(StandardCharsets.UTF_8);
ctx.writeAndFlush(new MessageProtocol(s.length,s));
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
cause.printStackTrace();
}
}
}
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>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
// 加入自定义分割符号
// ByteBuf delimiter = Unpooled.copiedBuffer("\r\n".getBytes());
// pipeline.addFirst(new DelimiterBasedFrameDecoder(8192, delimiter));
// 添加自定义协议编解码器
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;
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
// 连续发送10条数据
for (int i = 0; i < 10; i++) {
String msg = "今天天气冷, 打火锅" + i;
byte[] bytes = msg.getBytes(StandardCharsets.UTF_8);
// 使用自定义协议
MessageProtocol messageProtocol = new MessageProtocol(bytes.length, bytes);
ctx.writeAndFlush(messageProtocol);
}
}
@Override
protected void channelRead0(ChannelHandlerContext ctx, MessageProtocol msg) throws Exception {
byte[] bytes = msg.getContent();
// 接收服务器的返回
count++;
System.out.println("客户端第"+count+"次接收服务端的回送:" + new String(bytes, StandardCharsets.UTF_8));
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
ctx.close();
cause.printStackTrace();
}
}
}
发送10次
服务器端
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 ......
服务器第1次接收到来自客户端的数据:今天天气冷, 打火锅0
......
服务器第10次接收到来自客户端的数据:今天天气冷, 打火锅9
客户端
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.
客户端第1次接收服务端的回送:a6b69f1c-daba-435a-802a-c19a6350ca94
......
客户端第10次接收服务端的回送:5af5c297-8668-48aa-b8c4-35656142f591
ok,没有问题, 但是真的没有问题吗?答案是有问题
发送1000次
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
// 连续发送10条数据
for (int i = 0; i < 1000; i++) {
......
}
}
服务器端
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 ......
服务器第1次接收到来自客户端的数据:今天天气冷, 打火锅0
......
服务器第31次接收到来自客户端的数据:今天天气冷, 打火锅30
服务器第32次接收到来自客户端的数据:今天天气冷, 打火锅31
io.netty.handler.codec.DecoderException: java.lang.NegativeArraySizeException
at 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$5.run(SingleThreadEventExecutor.java:886)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NegativeArraySizeException
at com.dance.netty.netty.protocoltcp.MyMessageProtocolDecoder.decode(MyMessageProtocolDecoder.java:17)
at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:489)
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:428)
... 16 more
io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerIndex(1022) + length(4) exceeds writerIndex(1024): PooledUnsafeDirectByteBuf(ridx: 1022, widx: 1024, cap: 1024)
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:459)
at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:392)
at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:359)
at io.netty.handler.codec.ByteToMessageDecoder.channelInactive(ByteToMessageDecoder.java:342)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:224)
at io.netty.channel.DefaultChannelPipeline$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 ? 直接报错了, 数组下标越界, 读索引1022 + 长度4 > 写缩影1024了
这个是什么问题呢 ? 我看网上关于这个BUG的解决方案很少,基本没有, 好多都是贴问题的, 我翻了将近1个小时,才找到一个大佬写的一篇文章解决了, 感谢大佬
博客地址:
https://blog.csdn.net/u011035407/article/details/80454511
问题描述:
这样在刚开始的工作中数据包传输没有问题,不过数据包的大小超过512b的时候就会抛出异常了。
配合解码器DelimiterBasedFrameDecoder一起使用,在数据包的末尾使用换行符\n表示本次数据包已经结束,当DelimiterBasedFrameDecoder把数据切割之后,再使用ByteToMessageDecoder实现decode方法把数据流转换为Message对象。
我们在ChannelPipeline加入DelimiterBasedFrameDecoder解码器
客户端和服务器端都加
//使用\n作为分隔符
pipeline.addLast(new LoggingHandler(LogLevel.INFO));
pipeline.addLast(new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()));
在MessageToByteEncoder的实现方法encode()增加out.writeBytes(new byte[]{'\n'});
//在写出字节流的末尾增加\n表示数据结束
out.writeBytes(new byte[]{'\n'});
这时候就可以愉快的继续处理数据了。 等我还没有高兴半天的时候,问题又来了。还是一样的问题
等等等,,,怎么又报错了,不是已经加了黏包处理了吗??,解决问题把,首先看解析的数据包结构
+-------------------------------------------------+
| 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}. |
+--------+-------------------------------------------------+----------------+
接收到的数据是完整的没错,但是还是报错了,而且数据结尾的字节的确是0a,转化成字符就是\n没有问题啊。
在ByteToMessageDecoder的decode方法里打印ByteBuf buf的长度之后,问题找到了 长度 : 10
这就是说在进入到ByteToMessageDecoder这个解码器的时候,数据包已经只剩下10个长度了,那么长的数据被上个解码器DelimiterBasedFrameDecoder隔空劈开了- -。问题出现在哪呢,看上面那块字节流的字节,找到第11个字节,是0a。。。。因为不是标准的json格式,最前面使用了3个字节 加上2个int长度的属性,所以 数据包头应该是11个字节长。
而DelimiterBasedFrameDecoder在读到第11个字节的时候读成了\n,自然而然的就认为这个数据包已经结束了,而数据进入到ByteToMessageDecoder的时候就会因为规定的body长度不等于length长度而出现问题。
思来想去 不实用\n 这样的单字节作为换行符,很容易在数据流中遇到,转而使用\r\n俩字节来处理,而这俩字节出现在前面两个int长度中的几率应该很小。
在客户端和服务器端的pipeline中添加 以 "\r\n" 定义为边界的符号来标识数据包结束
//这里使用自定义分隔符
ByteBuf delimiter = Unpooled.copiedBuffer("\r\n".getBytes());
pipeline.addFirst(new DelimiterBasedFrameDecoder(8192, delimiter));
Server端
Client端
编码器中发送结束位置增加
//这里最后修改使用\r\n
out.writeBytes(new byte[]{'\r','\n'});
再次运行程序 数据包可以正常接收了。
服务器端
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 ......
服务器第1次接收到来自客户端的数据:今天天气冷, 打火锅0
......
服务器第999次接收到来自客户端的数据:今天天气冷, 打火锅998
服务器第1000次接收到来自客户端的数据:今天天气冷, 打火锅999
客户端
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.
客户端第1次接收服务端的回送:48fa6d78-8079-4700-b488-ca2af9eb3f8c
......
客户端第999次接收服务端的回送:581da47b-d77b-4972-af11-6d33057f6610
客户端第1000次接收服务端的回送:0014e906-69cb-4900-9409-f4d1af9148dd
以前使用netty的时候也仅限于和硬件交互,而当时的硬件受限于成本问题是一条一条处理数据包的,所以基本上不会考虑黏包问题
然后就是ByteToMessageDecoder和MessageToByteEncoder两个类是比较底层实现数据流处理的,并没有带有拆包黏包的处理机制,需要自己在数据包头规定包的长度,而且无法处理过大的数据包,因为我一开始首先使用了这种方式处理数据,所以后来就没有再换成DelimiterBasedFrameDecoder加 StringDecoder来解析数据包,最后使用json直接转化为对象。
FAQ 参考粘贴于大佬的博客,加自己的改动