Netty自定义数据包

怼烎@ 2021-12-13 13:49 353阅读 0赞

## 自定义数据包 ##

粘包现象：两个数据包连在一起，导致无法区分。  
分包现象：一个数据包中的数据被间隔。  
粘包和分包出现的原因是：没有一个稳定数据结构。

数据包的结构：  
自定义数据包=包头+模块号+命令号+长度+数据  
包头：4个字节  
模块号：2个字节short,区分请求类型  
命令号：2个字节short，区分具体请求  
长度：4个字节，描述数据部分字节长度  
数据：更加详细的信息

通过序列化方式将下列数据，转化成字节序列  
包头：通常是一个固定的量，使数据更加稳定  
自定义请求（响应）=模块号+命令号+请求数据部分

**以使用Netty ChannelBuffer序列化为例**  
**请求编码器**

public class RequestEncoder extends OneToOneEncoder{
    @Override
    protected Object encode(ChannelHandlerContext context, Channel channel, Object rs) throws Exception {
    	Request request = (Request)(rs);
    	
    	ChannelBuffer buffer = ChannelBuffers.dynamicBuffer();
    	//包头
    	buffer.writeInt(ConstantValue.FLAG);
    	//module
    	buffer.writeShort(request.getModule());
    	//cmd
    	buffer.writeShort(request.getCmd());
    	//长度
    	buffer.writeInt(request.getDataLength());
    	//data
    	if(request.getData() != null){
    		buffer.writeBytes(request.getData());
    	}		
    	return buffer;
    }

**请求解码器**  
frameDecoder协助解决粘包、分包问题

public class RequestDecoder extends FrameDecoder{
    	/**
    	 * 数据包基本长度
    	 */
    	public static int BASE_LENTH = 4 + 2 + 2 + 4;
    @Override
    protected Object decode(ChannelHandlerContext arg0, Channel arg1, ChannelBuffer buffer) throws Exception {
    	
    	//可读长度必须大于基本长度
    	if(buffer.readableBytes() >= BASE_LENTH){
    		//防止socket字节流攻击
    		if(buffer.readableBytes() > 2048){
    			buffer.skipBytes(buffer.readableBytes());
    		}
    		
    		//记录包头开始的index
    		int beginReader;
    		
    		while(true){
    			beginReader = buffer.readerIndex();
    			buffer.markReaderIndex();
    			if(buffer.readInt() == ConstantValue.FLAG){
    				break;
    			}
    			
    			//未读到包头，略过一个字节
    			buffer.resetReaderIndex();
    			buffer.readByte();
    			
    			//长度又变得不满足
    			if(buffer.readableBytes() < BASE_LENTH){
    				return null;
    			}
    		}
    		
    		//模块号
    		short module = buffer.readShort();
    		//命令号
    		short cmd = buffer.readShort();
    		//长度
    		int length = buffer.readInt();
    		
    		//判断请求数据包数据是否到齐
    		if(buffer.readableBytes() < length){
    			//还原读指针
    			buffer.readerIndex(beginReader);
    			return null;
    		}
    		
    		//读取data数据
    		byte[] data = new byte[length];
    		buffer.readBytes(data);
    		
    		Request request = new Request();
    		request.setModule(module);
    		request.setCmd(cmd);
    		request.setData(data);
    		
    		//继续往下传递 
    		return request;
    		
    	}
    	//数据包不完整，需要等待后面的包来
    	return null;
    }

## 结合Netty进行数据传递（选择自定义的报文结构） ##

**客户端**  
pipeline.addLast(“decoder”, new ResponseDecoder()); 用来解析响应,addLast追加  
pipeline.addLast(“encoder”, new RequestEncoder()); 用来编码请求  
在request中定义数据时，可以继承使用PB的序列化方式，或者自定义的序列化方式 request.setData(fightRequest.getBytes());

public class Client {
    
    public static void main(String[] args) throws InterruptedException {
    	
    	//服务类
    	ClientBootstrap bootstrap = new  ClientBootstrap();
    	
    	//线程池
    	ExecutorService boss = Executors.newCachedThreadPool();
    	ExecutorService worker = Executors.newCachedThreadPool();
    	
    	//socket工厂
    	bootstrap.setFactory(new NioClientSocketChannelFactory(boss, worker));
    	
    	//管道工厂
    	bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
    		
    		@Override
    		public ChannelPipeline getPipeline() throws Exception {
    			ChannelPipeline pipeline = Channels.pipeline();
    			pipeline.addLast("decoder", new ResponseDecoder());
    			pipeline.addLast("encoder", new RequestEncoder());
    			pipeline.addLast("hiHandler", new HiHandler());
    			return pipeline;
    		}
    	});
    	
    	//连接服务端
    	ChannelFuture connect = bootstrap.connect(new InetSocketAddress("127.0.0.1", 10101));
    	Channel channel = connect.sync().getChannel();
    	
    	System.out.println("client start");
    	
    	Scanner scanner = new Scanner(System.in);
    	while(true){
    		System.out.println("请输入");
    		int fubenId = Integer.parseInt(scanner.nextLine());
    		int count = Integer.parseInt(scanner.nextLine());
    		
    		FightRequest fightRequest = new FightRequest();
    		fightRequest.setFubenId(fubenId);
    		fightRequest.setCount(count);
    		
    		Request request = new Request();
    		request.setModule((short) 1);
    		request.setCmd((short) 1);
    		request.setData(fightRequest.getBytes());
    		//发送请求
    		channel.write(request);
    	}
    }

**服务器端**  
pipeline.addLast(“decoder”, new RequestDecoder()); 用来解析请求  
pipeline.addLast(“encoder”, new ResponseEncoder()); 用来编码响应

public class Server {
    
    public static void main(String[] args) {
    
    	//服务类
    	ServerBootstrap bootstrap = new ServerBootstrap();
    	
    	//boss线程监听端口，worker线程负责数据读写
    	ExecutorService boss = Executors.newCachedThreadPool();
    	ExecutorService worker = Executors.newCachedThreadPool();
    	
    	//设置niosocket工厂
    	bootstrap.setFactory(new NioServerSocketChannelFactory(boss, worker));
    	
    	//设置管道的工厂
    	bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
    		
    		@Override
    		public ChannelPipeline getPipeline() throws Exception {
    
    			ChannelPipeline pipeline = Channels.pipeline();
    			pipeline.addLast("decoder", new RequestDecoder());
    			pipeline.addLast("encoder", new ResponseEncoder());
    			pipeline.addLast("helloHandler", new HelloHandler());
    			return pipeline;
    		}
    	});
    	
    	bootstrap.bind(new InetSocketAddress(10101));
    	
    	System.out.println("start!!!");
    	
    }
    
    }

知识补充：  
TCP数据包结构=偏移量+窗口字段+端口号，总共占32个字节  
上面的自定义的最基础的占用12个字节  
![在这里插入图片描述][20190707213828905.gif]

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[20190707213828905.gif]: /images/20211213/badb9681a14e41f0a31d23d04bd82633.png
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