在tcp编程底层都有拆包和粘包的机制
拆包
当发送数据量过大时数据量会分多次发送
以前面helloWord代码为例
package com.liqiang.nettyTest2;public class nettyMain { ???public static void main(String[] args) { ???????new Thread(new Runnable() { ???????????@Override ???????????public void run() { ???????????????// TODO Auto-generated method stub ???????????????Server server = new Server(8081); ???????????????server.start(); ???????????} ???????}).start(); ???????new Thread(new Runnable() { ???????????????????????@Override ???????????public void run() { ???????????????// TODO Auto-generated method stub ???????????????Client client1=new Client("127.0.0.1", 8081); ???????????????client1.connection(); ???????????????client1.sendMsg("In this chapter you general, we recommend Java Concurrency in Practice by Brian Goetz. His book w" ?????????????????????????+ "ill give We’ve reached an exciting point—in the next chapter we’ll discuss bootstrapping, the process " ?????????????????????????+ "of configuring and connecting all of Netty’s components to bring your learned about threading models in ge" ?????????????????????????+ "neral and Netty’s threading model in particular, whose performance and consistency advantages we discuss" ?????????????????????????+ "ed in detail In this chapter you general, we recommend Java Concurrency in Practice by Brian Goetz. Hi" ?????????????????????????+ "s book will give We’ve reached an exciting point—in the next chapter we’ll discuss bootstrapping, the" ?????????????????????????+ " process of configuring and connecting all of Netty’s components to bring your learned about threading " ?????????????????????????+ "models in general and Netty’s threading model in particular, whose performance and consistency advantag" ?????????????????????????+ "es we discussed in detailIn this chapter you general, we recommend Java Concurrency in Practice by Bri" ?????????????????????????+ "an Goetz. His book will give We’ve reached an exciting point—in the next chapter;the counter is: 1 2222" ?????????????????????????+ "sdsa ddasd asdsadas dsadasdas"); ???????????} ???????}).start(); ???}}
打印
可以发现这里拆分成了2次发送
粘包
当发送数据量过小时会组合成一次发送
package com.liqiang.nettyTest2;public class nettyMain { ???public static void main(String[] args) { ???????new Thread(new Runnable() { ???????????@Override ???????????public void run() { ???????????????// TODO Auto-generated method stub ???????????????Server server = new Server(8081); ???????????????server.start(); ???????????} ???????}).start(); ???????new Thread(new Runnable() { ???????????????????????@Override ???????????public void run() { ???????????????// TODO Auto-generated method stub ???????????????Client client1=new Client("127.0.0.1", 8081); ???????????????client1.connection(); ???????????????for(int i=0;i<100;i++) { ???????????????????client1.sendMsg("d"); ???????????????} ???????????????????????????????????????????} ???????}).start(); ???}}
可以发现有时多条发送的数据会组合成一条发送
解决方案
netty提供了解码器来解决拆包和粘包的问题
LineBasedFrameDecoder
通过换行符来区分包
服务器端增加LineBasedFrameDecoder
package com.liqiang.nettyTest2;import io.netty.channel.ChannelInitializer;import io.netty.channel.socket.SocketChannel;import io.netty.handler.codec.LineBasedFrameDecoder;import io.netty.handler.codec.AsciiHeadersEncoder.NewlineType;import io.netty.handler.codec.string.StringDecoder;import io.netty.handler.codec.string.StringEncoder;public class ServerChannelInitializer extends ChannelInitializer<SocketChannel> { ???private Server server; ???public ServerChannelInitializer(Server server) { ???????this.server=server; ???} ???@Override ???protected void initChannel(SocketChannel channel) throws Exception { ???????// TODO Auto-generated method stub ???????channel.pipeline() ???????.addLast(new LineBasedFrameDecoder(2048))//2048是限制一个包的最大字节数。如果超过将会报异常 ???????.addLast("decoder",new StringDecoder())//接收到数据 自动将将buffer转换为String 避免自己再转 ???????.addLast("encoder",new StringEncoder())//发送数据 可以直接发送String 框架内部转换为buffer传输 ???????.addLast(new ServerHandle(server)); ???}}
客户端
package com.liqiang.nettyTest2;public class nettyMain { ???public static void main(String[] args) { ???????new Thread(new Runnable() { ???????????@Override ???????????public void run() { ???????????????// TODO Auto-generated method stub ???????????????Server server = new Server(8081); ???????????????server.start(); ???????????} ???????}).start(); ???????new Thread(new Runnable() { ???????????????????????@Override ???????????public void run() { ???????????????// TODO Auto-generated method stub ???????????????Client client1=new Client("127.0.0.1", 8081); ???????????????client1.connection(); ???????????????client1.sendMsg("In this chapter you general, we recommend Java Concurrency in Practice by Brian Goetz. His book w" ?????????????????????????+ "ill give We’ve reached an exciting point—in the next chapter we’ll discuss bootstrapping, the process " ?????????????????????????+ "of configuring and connecting all of Netty’s components to bring your learned about threading models in ge" ?????????????????????????+ "neral and Netty’s threading model in particular, whose performance and consistency advantages we discuss" ?????????????????????????+ "ed in detail In this chapter you general, we recommend Java Concurrency in Practice by Brian Goetz. Hi" ?????????????????????????+ "s book will give We’ve reached an exciting point—in the next chapter we’ll discuss bootstrapping, the" ?????????????????????????+ " process of configuring and connecting all of Netty’s components to bring your learned about threading " ?????????????????????????+ "models in general and Netty’s threading model in particular, whose performance and consistency advantag" ?????????????????????????+ "es we discussed in detailIn this chapter you general, we recommend Java Concurrency in Practice by Bri" ?????????????????????????+ "an Goetz. His book will give We’ve reached an exciting point—in the next chapter;the counter is: 1 2222" ?????????????????????????+ "sdsa ddasd asdsadas dsadasdas"+System.getProperty("line.separator"));//System.getProperty("line.separator") 兼容linux和windows的区别 ???????????} ???????}).start(); ???}}
如果发送数据忘记拼换行符 服务器将不会有任何打印
DelimiterBasedFrameDecoder
通过指定符号区分
服务器端
package com.liqiang.nettyTest2;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelInitializer;import io.netty.channel.socket.SocketChannel;import io.netty.handler.codec.LineBasedFrameDecoder;import io.netty.handler.codec.AsciiHeadersEncoder.NewlineType;import io.netty.handler.codec.DelimiterBasedFrameDecoder;import io.netty.handler.codec.string.StringDecoder;import io.netty.handler.codec.string.StringEncoder;public class ServerChannelInitializer extends ChannelInitializer<SocketChannel> { ???private Server server; ???public ServerChannelInitializer(Server server) { ???????this.server=server; ???} ???@Override ???protected void initChannel(SocketChannel channel) throws Exception { ???????// TODO Auto-generated method stub ???????channel.pipeline() ???????.addLast(new DelimiterBasedFrameDecoder(2048,Unpooled.copiedBuffer("$$__".getBytes())))//$__为包的分隔符2048是限制一个包的最大字节数。如果超过将会报异常 ???????.addLast("decoder",new StringDecoder())//接收到数据 自动将将buffer转换为String 避免自己再转 ???????.addLast("encoder",new StringEncoder())//发送数据 可以直接发送String 框架内部转换为buffer传输 ???????.addLast(new ServerHandle(server)); ???}}
客户端
package com.liqiang.nettyTest2;public class nettyMain { ???public static void main(String[] args) { ???????new Thread(new Runnable() { ???????????@Override ???????????public void run() { ???????????????// TODO Auto-generated method stub ???????????????Server server = new Server(8081); ???????????????server.start(); ???????????} ???????}).start(); ???????new Thread(new Runnable() { ???????????????????????@Override ???????????public void run() { ???????????????// TODO Auto-generated method stub ???????????????Client client1=new Client("127.0.0.1", 8081); ???????????????client1.connection(); ???????????????client1.sendMsg("In this chapter you general, we recommend Java Concurrency in Practice by Brian Goetz. His book w" ?????????????????????????+ "ill give We’ve reached an exciting point—in the next chapter we’ll discuss bootstrapping, the process " ?????????????????????????+ "of configuring and connecting all of Netty’s components to bring your learned about threading models in ge" ?????????????????????????+ "neral and Netty’s threading model in $$__particular, whose performance and consistency advantages we discuss" ?????????????????????????+ "ed in detail In this chapter you general, we recommend Java Concurrency in Practice by Brian Goetz. Hi" ?????????????????????????+ "s book will give We’ve reached an exciting point—in the next chapter we’ll discuss bootstrapping, the" ?????????????????????????+ " process of configuring and connecting all $$__of Netty’s components to bring your learned about threading " ?????????????????????????+ "models in general and Netty’s threading model in particular, whose performance and consistency advantag" ?????????????????????????+ "es we discussed in detailIn this chapter you general, we recommend Java Concurrency in Practice by Bri" ?????????????????????????+ "an Goetz. His book will give We’ve reached an exciting point—in the next chapter;the counter is: 1 2222" ?????????????????????????+ "sdsa ddasd asdsadas dsadasdas$__"); ???????????} ???????}).start(); ???}}
根据$__数据被拆分成了三个包
netty 拆包和粘包 (三)
原文地址:https://www.cnblogs.com/LQBlog/p/9147759.html