Netty 01 | 简介与helloworld

传统的Socket IO 比较

传送IO特点

• 阻塞点
  server.accept();
  inputStream.read(bytes);

• 单线程情况下只能有一个客户端
  用线程池可以有多个客户端连接，但是非常消耗性能

NIO的特点

ServerSocketChannel ServerSocket

SocketChannel Socket

Selector

SelectionKey

NIO的一些疑问

1. 客户端关闭的时候会抛出异常，死循环
   解决方案

	int read = channel.read(buffer);
		if(read > 0){
			byte[] data = buffer.array();
			String msg = new String(data).trim();
			System.out.println("服务端收到信息：" + msg);
			
			//回写数据
			ByteBuffer outBuffer = ByteBuffer.wrap("好的".getBytes());
			channel.write(outBuffer);// 将消息回送给客户端
		}else{
			System.out.println("客户端关闭");
			key.cancel();
		}

2. selector.select();阻塞，那为什么说nio是非阻塞的IO？

   selector.select()
   selector.select(1000);不阻塞
   selector.wakeup();也可以唤醒selector
   selector.selectNow();也可以立马返还

3. SelectionKey.OP_WRITE是代表什么意思
   OP_WRITE表示底层缓冲区是否有空间，是则响应返还true

netty可以运用在那些领域？

1. 分布式进程通信
   例如: hadoop、dubbo、akka等具有分布式功能的框架，底层RPC通信都是基于netty实现的，这些框架使用的版本通常都还在用netty3.x
2. CS IM通信
3. 游戏服务器开发
   最新的游戏服务器有部分公司可能已经开始采用netty4.x 或 netty5.x

1、netty服务端hello world案例

SimpleChannelHandler 处理消息接收和写
{
  messageReceived接收消息

  channelConnected新连接，通常用来检测IP是否是黑名单

  channelDisconnected链接关闭，可以再用户断线的时候清楚用户的缓存数据等
}

package com.server;

import java.net.InetSocketAddress;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;
/**
 * netty服务端入门
 *
 */
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 StringDecoder());//上游
				pipeline.addLast("encoder", new StringEncoder());//下游
				pipeline.addLast("helloHandler", new HelloHandler());
				return pipeline;
			}
		});
		
		bootstrap.bind(new InetSocketAddress(10101));
		
		System.out.println("start!!!");
		
	}

}

2、netty客户端hello world案例

channelDisconnected与channelClosed的区别？

channelDisconnected只有在连接建立后断开才会调用
channelClosed无论连接是否成功都会调用关闭资源

package com.client;

import java.net.InetSocketAddress;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import org.jboss.netty.bootstrap.ClientBootstrap;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringDecoder;
import org.jboss.netty.handler.codec.string.StringEncoder;
/**
 * netty客户端入门
 *
 */
public class Client {

	public static void main(String[] args) {
		
		//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 StringDecoder());
				pipeline.addLast("encoder", new StringEncoder());
				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.getChannel();//与 HiHandler 是统一个Channel，在这里与Hihandler 中处理一样
		
		System.out.println("client start");
		
		Scanner scanner = new Scanner(System.in);
		while(true){
			System.out.println("请输入");
			channel.write(scanner.next());
		}
	}

}