netty之心跳机制

　　1、心跳机制，在netty3和netty5上面都有。但是写法有些不一样。

　　2、心跳机制在服务端和客户端的作用也是不一样的。对于服务端来说：就是定时清除那些因为某种原因在一定时间段内没有做指定操作的客户端连接。对于服务端来说：用来检测是否断开连接，然后尝试重连等问题。游戏上面也可以来监控延时问题。

　　3、我这边只写了服务端的心跳用法，客户端基本差不多。

　　1）netty3的写法

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;
import org.jboss.netty.handler.timeout.IdleStateHandler;
import org.jboss.netty.util.HashedWheelTimer;

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

public class Server {

    public static void main(String[] args) {

        //声明服务类
        ServerBootstrap serverBootstrap = new ServerBootstrap();

        //设定线程池
        ExecutorService boss = Executors.newCachedThreadPool();
        ExecutorService work = Executors.newCachedThreadPool();

        //设置工厂
        serverBootstrap.setFactory(new NioServerSocketChannelFactory(boss,work));

        //设置管道流
        serverBootstrap.setPipelineFactory(new ChannelPipelineFactory() {
            @Override
            public ChannelPipeline getPipeline() throws Exception {
                ChannelPipeline channelPipeline = Channels.pipeline();
                //添加处理方式
                channelPipeline.addLast("idle",new IdleStateHandler(new HashedWheelTimer(),5,5,10));
                channelPipeline.addLast("decode",new StringDecoder());
                channelPipeline.addLast("encode",new StringEncoder());
                channelPipeline.addLast("server",new ServerHandler());
                return channelPipeline;
            }
        });

        //设置端口
        serverBootstrap.bind(new InetSocketAddress(9000));
    }
}

　　备注：这里和之前有变化的就是管道里面多加了一个心跳，实际的处理还是在处理类里面

　channelPipeline.addLast("idle",new IdleStateHandler(new HashedWheelTimer(),5,5,10));

import org.jboss.netty.channel.*;
import org.jboss.netty.handler.timeout.IdleState;
import org.jboss.netty.handler.timeout.IdleStateEvent;

public class ServerHandler extends SimpleChannelHandler {

    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
        System.out.println("client:"+e.getMessage());
        ctx.getChannel().write(e.getMessage());
        super.messageReceived(ctx, e);
    }

    @Override
    public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
        if (e instanceof IdleStateEvent) {
            if (((IdleStateEvent)e).getState() == IdleState.ALL_IDLE) {
                ChannelFuture channelFuture = ctx.getChannel().write("Time out,You will close");
                channelFuture.addListener(channelFuture1 -> ctx.getChannel().close());
            }
        } else {
            super.handleUpstream(ctx, e);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
        super.exceptionCaught(ctx, e);
    }

    @Override
    public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        super.channelConnected(ctx, e);
    }

    @Override
    public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        super.channelDisconnected(ctx, e);
    }

    @Override
    public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
        super.channelClosed(ctx, e);
    }
}

　　说明：这里是用SimpleChannelHandler里面给出的事件处理来实现的。方法为handleUpstream

　　2）netty5的写法和netty3差不多

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.handler.timeout.IdleStateHandler;

public class Server {

    public static void main(String[] args) {
        //服务类
        ServerBootstrap serverBootstrap = new ServerBootstrap();
        //声明两个线程池
        EventLoopGroup boss = new NioEventLoopGroup();
        EventLoopGroup work = new NioEventLoopGroup();

        try {
            //设置线程组
            serverBootstrap.group(boss,work);
            //设置服务socket工厂
            serverBootstrap.channel(NioServerSocketChannel.class);
            //设置管道
            serverBootstrap.childHandler(new ChannelInitializer<Channel>() {
                protected void initChannel(Channel channel) throws Exception {
                    channel.pipeline().addLast(new IdleStateHandler(5,5,10));
                    channel.pipeline().addLast(new StringDecoder());
                    channel.pipeline().addLast(new StringEncoder());
                    channel.pipeline().addLast(new ServerHandler());
                }
            });
            //设置服务器连接数
            serverBootstrap.option(ChannelOption.SO_BACKLOG,2048);
            //设置tcp延迟状态
            serverBootstrap.option(ChannelOption.TCP_NODELAY,true);
            //设置激活状态，2小时清除
            serverBootstrap.option(ChannelOption.SO_KEEPALIVE,true);
            //监听端口
            ChannelFuture channelFuture = serverBootstrap.bind(9000);
            //等待服务器关闭
            channelFuture.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //关闭线程池
            boss.shutdownGracefully();
            work.shutdownGracefully();
        }

    }

}

import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.timeout.IdleState;
import io.netty.handler.timeout.IdleStateEvent;

public class ServerHandler extends SimpleChannelInboundHandler<String> {

    //接收消息并处理
    protected void messageReceived(ChannelHandlerContext channelHandlerContext, String s) throws Exception {
        System.out.println(s);
        channelHandlerContext.writeAndFlush("hello client");
    }

    @Override
    public void userEventTriggered(final ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            if (((IdleStateEvent)evt).state() == IdleState.ALL_IDLE) {
                ChannelFuture channelFuture = ctx.writeAndFlush("Time out,You will close");
                channelFuture.addListener(new ChannelFutureListener() {
                    public void operationComplete(ChannelFuture channelFuture) throws Exception {
                        ctx.channel().close();
                    }
                });
            }
        } else {
            super.userEventTriggered(ctx, evt);
        }
    }
}