WebSockets MQTT Subscription Example

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#include "clientsubscription.h" #include <QtCore/QCoreApplication> #include <QtCore/QLoggingCategory> Q_LOGGING_CATEGORY(lcWebSocketMqtt, "qtdemo.websocket.mqtt") ClientSubscription::ClientSubscription(QObject *parent) : QObject(parent) { connect(this, &ClientSubscription::errorOccured, qApp, &QCoreApplication::quit); } void ClientSubscription::setUrl(const QUrl &url) { m_url = url; } void ClientSubscription::setTopic(const QString &topic) { m_topic = topic; } void ClientSubscription::setVersion(int v) { m_version = v; } void ClientSubscription::connectAndSubscribe() { qCDebug(lcWebSocketMqtt) << "Connecting to broker at " << m_url; m_device.setUrl(m_url); m_device.setProtocol(m_version == 3 ? "mqttv3.1" : "mqtt"); connect(&m_device, &WebSocketIODevice::socketConnected, this, [this]() { qCDebug(lcWebSocketMqtt) << "WebSocket connected, initializing MQTT connection."; m_client.setProtocolVersion(m_version == 3 ? QMqttClient::MQTT_3_1 : QMqttClient::MQTT_3_1_1); m_client.setTransport(&m_device, QMqttClient::IODevice); connect(&m_client, &QMqttClient::connected, this, [this]() { qCDebug(lcWebSocketMqtt) << "MQTT connection established"; m_subscription = m_client.subscribe(m_topic); if (!m_subscription) { qDebug() << "Failed to subscribe to " << m_topic; emit errorOccured(); } connect(m_subscription, &QMqttSubscription::stateChanged, [](QMqttSubscription::SubscriptionState s) { qCDebug(lcWebSocketMqtt) << "Subscription state changed:" << s; }); connect(m_subscription, &QMqttSubscription::messageReceived, [this](QMqttMessage msg) { handleMessage(msg.payload()); }); }); m_client.connectToHost(); }); if (!m_device.open(QIODevice::ReadWrite)) qDebug() << "Could not open socket device"; } void ClientSubscription::handleMessage(const QByteArray &msgContent) { // Should happen when the internal device has ready read? qInfo() << "New message:" << msgContent; }