@Slf4j
public class HeartBeatServerHandler extends IdleStateHandler {
    private static final int READ_IDLE_GAP = 150; // 最大空閑時(shí)間(s)
    public HeartBeatServerHandler() {
        super(READ_IDLE_GAP, 0, 0, TimeUnit.SECONDS);
    }
    @Override
    protected void channelIdle(ChannelHandlerContext ctx, IdleStateEvent evt) throws Exception {
        log.info("{}秒內(nèi)未讀到數(shù)據(jù)，關(guān)閉連接", READ_IDLE_GAP);
        // 其他處理，如關(guān)閉會(huì)話
    }
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        // 判斷消息實(shí)例
        if (!(msg instanceof MessageProtos.Message message)) {
            super.channelRead(ctx, msg);
            return;
        }
        if (message.getType() == MessageProtos.HeadType.HEART_BEAT) {
            if (ctx.channel().isActive()) {
                // 將心跳數(shù)據(jù)包直接回給客戶端
                ctx.writeAndFlush(msg);
            }
        }
        super.channelRead(ctx, msg);
    }
}

@Slf4j
public class HeartBeatClientHandler extends ChannelInboundHandlerAdapter {
    // 心跳的時(shí)間間隔，單位為秒
    private static final int HEART_BEAT_INTERVAL = 50;
    // 在Handler業(yè)務(wù)處理器被加入到流水線時(shí)開(kāi)始發(fā)送心跳數(shù)據(jù)包
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        ClientSession session = ctx.channel().attr(ClientSession.CLIENT_SESSION).get();
        MessageProtos.MessageHeartBeat heartBeat =
                MessageProtos.MessageHeartBeat.newBuilder()
                        .setSeq(0)
                        .setJson("{\"from\":\"client\"}")
                        .setUid(session.getUserDTO().getUserId())
                        .build();
        MessageProtos.Message message = MessageProtos.Message.newBuilder()
                .setType(MessageProtos.HeadType.HEART_BEAT)
                .setSessionId(session.getSessionId())
                .setMessageHeartBeat(heartBeat)
                .build();
        heartBeat(ctx, message);
        super.handlerAdded(ctx);
    }
    private void heartBeat(ChannelHandlerContext ctx, MessageProtos.Message message) {
        // 提交在給定延遲后啟用的一次性任務(wù)。
        ctx.executor().schedule(() -> {
            if (ctx.channel().isActive()) {
                log.info("發(fā)送心跳消息給服務(wù)端");
                ctx.writeAndFlush(message);
                // 遞歸調(diào)用，發(fā)送下一次的心跳
                heartBeat(ctx, message);
            }
        }, HEART_BEAT_INTERVAL, TimeUnit.SECONDS);
    }
    // 接收到服務(wù)器的心跳回寫
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if (!(msg instanceof MessageProtos.Message message)) {
            super.channelRead(ctx, msg);
            return;
        }
        if (message.getType() == MessageProtos.HeadType.HEART_BEAT) {
            log.info("收到會(huì)寫的心跳信息");
        } else {
            super.channelRead(ctx, msg);
        } 
    }
}