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pipeline.addLast("IdleHandler", new IdleStateHandler(3, 5, 7, TimeUnit.SECONDS));
pipeline.addLast("UserIdleHandler", new HeartbeatServerHandler());

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/**
 * 这个处理器会处理 {@link IdleStateHandler} 这个心跳检测传递来的数据
 *
 * @author L
 */
public class HeartbeatServerHandler extends ChannelInboundHandlerAdapter {

    Logger log = LoggerUtils.getLogger(HeartbeatServerHandler.class);

    /**
     * 事件触发
     *
     * @param ctx 上下文信息
     * @param evt 触发的事件
     */
    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) {
        if (evt instanceof IdleStateEvent) {
            // 向下转型
            IdleStateEvent idleStateEvent = (IdleStateEvent) evt;

            switch (idleStateEvent.state()) {
                case ALL_IDLE:
                    log.info("读写空闲");
                    break;
                case READER_IDLE:
                    log.info("读空闲");
                    break;
                case WRITER_IDLE:
                    log.info("写空闲");
                    break;
            }
        }
    }
}

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package com.netty.heartbeat;

import com.utils.LoggerUtils;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
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 org.slf4j.Logger;

import java.util.concurrent.TimeUnit;

/**
 * @author L
 */
public class HeartbeatServer {

    Logger log = LoggerUtils.getLogger(HeartbeatServer.class);

    public void init() throws InterruptedException {

        EventLoopGroup boosGroup = new NioEventLoopGroup();
        EventLoopGroup workGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.channel(NioServerSocketChannel.class)
                    .group(boosGroup, workGroup)
                    // 添加一个处理器 （日志处理器）
                    .handler(new LoggingHandler(LogLevel.INFO))
                    // work 工作的处理器
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) {
                            ChannelPipeline pipeline = ch.pipeline();
                            // {@link IdleStateHandler} netty 提供的处理空闲状态的处理器
                            // readerIdleTime 读空闲 {多长时间没有读就会发送一个心跳检测包，检查是否链接}
                            // writerIdleTime 写空闲 {多长时间没有写就会发送一个心跳检测包，检查是否链接}
                            // allIdleTime 读写空闲 {多长时间既没有读也没有写就会发送一个心跳检测包，检查是否链接}
                            // idle handler trigger 以后就会把结果传递给下一个 handler 处理
                            pipeline.addLast("", new IdleStateHandler(3, 5, 7, TimeUnit.SECONDS));
                            pipeline.addLast("UserIdleHandler", new HeartbeatServerHandler());
                        }
                    });

            ChannelFuture channelFuture = bootstrap.bind(6666).sync();
            // 添加监听器
            channelFuture.addListener(future -> {
                if (future.isDone()) log.info("服务器绑定端口成功");
            });
            channelFuture.channel().closeFuture().sync();
        } finally {
            boosGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        }
    }
}