Netty5 服务端和客户端

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本文详细介绍Netty 5服务端及客户端的实现方法，包括关键配置与消息处理流程，并探讨了多连接客户端的设计方案。

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Netty5 服务端和客户端

概述

netty 5 已经放弃掉了,作为学习netty4和5的差别不大,本例子是基于netty5

https://github.com/netty/netty/issues/4466

线程安全

一个thread + 队列 == 一个单线程线程池。线程安全的，任务是线性串行执行的
线程安全，不会产生阻塞效应，使用对象组
线程不安全，会产生阻塞效应，使用对象池

Figure 1. 对象池

Figure 2. 对象组

writeAndFlush 发送消息线程安全

其中 EventExecutor executor 是 NioEventLoop 线程安全

public final class NioEventLoop extends SingleThreadEventLoop

代码

Server

/**
 * netty5服务端
 *
 *
 */
public class Server {

	public static void main(String[] args) {
		//服务类
		ServerBootstrap bootstrap = new ServerBootstrap();

		//boss和worker
		EventLoopGroup boss = new NioEventLoopGroup();
		EventLoopGroup worker = new NioEventLoopGroup();

		try {
			//设置线程池
			bootstrap.group(boss, worker);

			//设置socket工厂、
			bootstrap.channel(NioServerSocketChannel.class);

			//设置管道工厂
			bootstrap.childHandler(new ChannelInitializer<Channel>() {

				@Override
				protected void initChannel(Channel ch) throws Exception {
					ch.pipeline().addLast(new StringDecoder());
					ch.pipeline().addLast(new StringEncoder());
					ch.pipeline().addLast(new ServerHandler());
				}
			});

			//netty3中对应设置如下
			//bootstrap.setOption("backlog", 1024);
			//bootstrap.setOption("tcpNoDelay", true);
			//bootstrap.setOption("keepAlive", true);
			//设置参数，TCP参数
			bootstrap.option(ChannelOption.SO_BACKLOG, 2048);//serverSocketchannel的设置，链接缓冲池的大小
			bootstrap.childOption(ChannelOption.SO_KEEPALIVE, true);//socketchannel的设置,维持链接的活跃，清除死链接
			bootstrap.childOption(ChannelOption.TCP_NODELAY, true);//socketchannel的设置,关闭延迟发送

			//绑定端口
			ChannelFuture future = bootstrap.bind(10101);

			System.out.println("start");

			//等待服务端关闭
			future.channel().closeFuture().sync();

		} catch (Exception e) {
			e.printStackTrace();
		} finally{
			//释放资源
			boss.shutdownGracefully();
			worker.shutdownGracefully();
		}
	}
}

ServerHandler

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
/**
 * 服务端消息处理
 *
 *
 */
public class ServerHandler extends SimpleChannelInboundHandler<String> {

	@Override
	protected void messageReceived(ChannelHandlerContext ctx, String msg) throws Exception {

		System.out.println(msg);

		ctx.channel().writeAndFlush("hi");
		ctx.writeAndFlush("hi");
	}

	/**
	 * 新客户端接入
	 */
	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception {
		System.out.println("channelActive");
	}

	/**
	 * 客户端断开
	 */
	@Override
	public void channelInactive(ChannelHandlerContext ctx) throws Exception {
		System.out.println("channelInactive");
	}

	/**
	 * 异常
	 */
	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
		cause.printStackTrace();
	}


}

Client

import java.io.BufferedReader;
import java.io.InputStreamReader;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

/**
 * netty5的客户端
 *
 *
 */
public class Client {

	public static void main(String[] args) {
		//服务类
		Bootstrap bootstrap = new Bootstrap();

		//worker
		EventLoopGroup worker = new NioEventLoopGroup();

		try {
			//设置线程池
			bootstrap.group(worker);

			//设置socket工厂、
			bootstrap.channel(NioSocketChannel.class);

			//设置管道
			bootstrap.handler(new ChannelInitializer<Channel>() {

				@Override
				protected void initChannel(Channel ch) throws Exception {
					ch.pipeline().addLast(new StringDecoder());
					ch.pipeline().addLast(new StringEncoder());
					ch.pipeline().addLast(new ClientHandler());
				}
			});

			ChannelFuture connect = bootstrap.connect("127.0.0.1", 10101);

			BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
			while(true){
				System.out.println("请输入：");
				String msg = bufferedReader.readLine();
				connect.channel().writeAndFlush(msg);
			}

		} catch (Exception e) {
			 e.printStackTrace();
		} finally{
			worker.shutdownGracefully();
		}
	}
}

ClientHandler

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
/**
 * 客户端消息处理
 *
 *
 */
public class ClientHandler extends SimpleChannelInboundHandler<String> {

	@Override
	protected void messageReceived(ChannelHandlerContext ctx, String msg) throws Exception {
		System.out.println("客户端收到消息:"+msg);
	}

}

多连接客户端

MultClient

其中 synchronized(channel) 可以采用单任务队列的方式

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

/**
 * 多连接客户端
 *
 *
 */
public class MultClient {

	/**
	 * 服务类
	 */
	private Bootstrap bootstrap = new Bootstrap();

	/**
	 * 会话
	 */
	private List<Channel> channels = new ArrayList<>();

	/**
	 * 引用计数
	 */
	private final AtomicInteger index = new AtomicInteger();

	/**
	 * 初始化
	 * @param count
	 */
	public void init(int count){

		//worker
		EventLoopGroup worker = new NioEventLoopGroup();

		//设置线程池
		bootstrap.group(worker);

		//设置socket工厂、
		bootstrap.channel(NioSocketChannel.class);

		//设置管道
		bootstrap.handler(new ChannelInitializer<Channel>() {

			@Override
			protected void initChannel(Channel ch) throws Exception {
				ch.pipeline().addLast(new StringDecoder());
				ch.pipeline().addLast(new StringEncoder());
				ch.pipeline().addLast(new ClientHandler());
			}
		});

		for(int i=1; i<=count; i++){
			ChannelFuture future = bootstrap.connect("192.168.0.103", 10101);
			channels.add(future.channel());
		}
	}

	/**
	 * 获取会话
	 * @return
	 */
	public Channel nextChannel(){
		return getFirstActiveChannel(0);
	}


	private Channel getFirstActiveChannel(int count){
		Channel channel = channels.get(Math.abs(index.getAndIncrement() % channels.size()));
		if(!channel.isActive()){
			//重连
			reconnect(channel);
			if(count >= channels.size()){
				throw new RuntimeException("no can use channel");
			}
			return getFirstActiveChannel(count + 1);
		}
		return channel;
	}

	/**
	 * 重连
	 * @param channel
	 */
	private void reconnect(Channel channel){
		synchronized(channel){
			if(channels.indexOf(channel) == -1){
				return ;
			}

			Channel newChannel = bootstrap.connect("192.168.0.103", 10101).channel();
			channels.set(channels.indexOf(channel), newChannel);
		}
	}

}

Start

import java.io.BufferedReader;
import java.io.InputStreamReader;
/**
 * 启动类
 *
 *
 */
public class Start {

	public static void main(String[] args) {

		MultClient client = new MultClient();
		client.init(5);

		BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
		while(true){
			try {
				System.out.println("请输入:");
				String msg = bufferedReader.readLine();
				client.nextChannel().writeAndFlush(msg);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}

}