netty 心跳检测机制案例

　　当服务器超过 3 秒 没有读时，提示“读空闲”；当服务器超过 5 秒没有写操作时，提示“写空闲”；当服务器超过 7 秒没有读或者写操作时，提示“读写空闲”。

 　　HeartBeatServer

package com.oy.heartbeat;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import io.netty.handler.timeout.IdleStateHandler;

import java.util.concurrent.TimeUnit;

public class HeartBeatServer {

    private int port;
    public HeartBeatServer(int port) {
        this.port = port;
    }

    public static void main(String[] args) throws Exception {
        new HeartBeatServer(8001).run();
    }

    public void run() throws Exception {
        EventLoopGroup boss = new NioEventLoopGroup(1);
        EventLoopGroup work = new NioEventLoopGroup();

        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap
                    .channel(NioServerSocketChannel.class)
                    .group(boss, work)
                    .handler(new LoggingHandler(LogLevel.DEBUG)) // 在 bossGroup 添加一个日志处理器
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            ChannelPipeline pipeline = socketChannel.pipeline();
                            /*
                             * IdleStateHandler: netty 提供的处理空闲状态的处理器
                             * long readerIdleTime: 多长时间没有读，就会发送一个心跳检查是否连接
                             * long writerIdleTime: 多长时间没有写，就会发送一个心跳检查是否连接
                             * long allIdleTime: 多长时间没有读写，就会发送一个心跳检查是否连接
                             */
                            pipeline.addLast(new IdleStateHandler(3,5,7, TimeUnit.SECONDS));
                            // 当 IdleStateEvent 触发后，就会传递给管道的下一个 handler 进行处理
                            // 通过调用（触发）下一个 handler 的 userEventTriggered()
                            // 添加对空闲检测进一步处理的自定义 handler
                            pipeline.addLast(new HeartBeatServerHandler());
                        }
                    });

            // 绑定端口，启动服务
            ChannelFuture future = bootstrap.bind(port).sync();
            System.out.println("server started and listen " + port);
            // 监听关闭
            future.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            boss.shutdownGracefully();
            work.shutdownGracefully();
        }
    }
}

　　HeartBeatServerHandler

package com.oy.heartbeat;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.handler.timeout.IdleStateEvent;

public class HeartBeatServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            IdleStateEvent event = (IdleStateEvent) evt;
            String eventType = null;
            switch (event.state()) {
                case READER_IDLE:
                    eventType = "读空闲";
                    break;
                case WRITER_IDLE:
                    eventType = "写空闲";
                    break;
                case ALL_IDLE:
                    eventType = "读写空闲";
                    break;
            }
            System.out.println(ctx.channel().remoteAddress() + "--超时事件: " + eventType);

            // 如果发生空闲，关闭通道
            //ctx.channel().close();
        }
    }
}

　　

　　HeartBeatClient

package com.oy.heartbeat;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.util.Scanner;

public class HeartBeatClient {
    private static final String HOST = "127.0.0.1";
    private static final int PORT = 8001;

    public static void main(String[] args) {
        new HeartBeatClient().run(HOST, PORT);
    }

    public void run(String host, int port) {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap client = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast("decoder", new StringDecoder()); // 解码器
                            pipeline.addLast("encoder", new StringEncoder()); // 编码器
                            ch.pipeline().addLast(new HeartBeatClientHandler());
                        }
                    });

            ChannelFuture future = client.connect(host, port).sync();
            System.out.println("--------------" + future.channel().localAddress() + "--------------");

            Channel channel = future.channel();
            // 客户端输入信息
            Scanner scanner = new Scanner(System.in);
            while (scanner.hasNext()) {
                String msg = scanner.nextLine();
                channel.writeAndFlush(msg + "\r\n");
            }

            future.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            group.shutdownGracefully();
        }
    }
}

　　HeartBeatClientHandler

package com.oy.heartbeat;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class HeartBeatClientHandler extends SimpleChannelInboundHandler<String> {

    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String msg) throws Exception {
        System.out.println(msg);
    }
}

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