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从连接和定时器看起

这段摘自 mqtthandler.cpp，先建立 MQTT 客户端，把连接成功、订阅成功和收到消息接到对应处理函数上。

断线重连间隔设成 3000 ms，调用连接后再等 3 秒检查状态。模拟温湿度的定时器间隔是 1000 ms，下面可以看到它和发布函数怎么连起来。

底层用的是现成的 QMQTT 库，这段展示我整理的业务接线，数据来自模拟，硬件联调还没做。

源码摘录

cpp

#include "mqtthandler.h"
#include <QTimer>
#include <QJsonDocument>
#include <QJsonObject>
#include <QRandomGenerator>
#include <qmqtt_client.h>

#define TOPIC_DATA_UP       "/app/data/up"
#define TOPIC_DATA_DOWN     "/app/data/down"
#define TOPIC_CTL_UP        "/app/control/up"
#define TOPIC_CTL_DOWN      "/app/control/down"

MqttHandler::MqttHandler(QObject *parent) : QObject(parent)
{
    client = new QMQTT::Client();
    client->setClientId("home-app");
    //断线或连不上时自动重连，等 broker 启动后可自动接上
    client->setAutoReconnect(true);
    client->setAutoReconnectInterval(3000);

    connect(client, SIGNAL(connected()), this, SLOT(doConnected()));

    connect(client, SIGNAL(subscribed(QString, quint8)),\
            this, SLOT(doSubscribed(QString, quint8)));

    connect(client,SIGNAL(received(QMQTT::Message)),\
            this,SLOT(doDataReceived(QMQTT::Message)));

    //温湿度模拟定时器：连接成功后每隔1秒发布一条模拟数据
    simTimer = new QTimer(this);
    simTimer->setInterval(1000);
    connect(simTimer, SIGNAL(timeout()), this, SLOT(publishSimulation()));
}

void MqttHandler::connectToHost()
{
    client->connectToHost();

    //3s后检测一下连接状态
    QTimer::singleShot(3000, this, SLOT(detectState()));
}