thermostat: monitor the mqtt connection

soft/thermostat/inc/mqttclient.h

@@ -33,6 +33,7 @@ public slots:
 	void onStateChanged(ClientState state);
 	void onDisconnected(void);
 	void allHeatersOn(bool on);
+	void onConnectTimeout(void);
 
 signals:
 	void new_temperature(int idx, double val);

soft/thermostat/src/mqttclient.cpp

@@ -16,6 +16,8 @@
 #include "mqttclient.h"
 #include "settings.h"
 
+#define TIMER_PERIOD_MS 30000
+
 MQTTClient::MQTTClient(const QString& host, int port, QObject* parent)
 	: QMqttClient(parent)
 {
@@ -32,19 +34,48 @@ MQTTClient::MQTTClient(const QString& host, int port, QObject* parent)
 	connect(this, SIGNAL(stateChanged(ClientState)),
 		this, SLOT(onStateChanged(ClientState)));
 
+	connect(&m_timer, SIGNAL(timeout()), this, SLOT(onConnectTimeout()));
+	m_timer.start(TIMER_PERIOD_MS);
 }
 
 MQTTClient::~MQTTClient() {
 }
 
+/*
+ * the QMqttClient doesn't handle auto-reconnection.
+ * It can stay in the connecting state for ever, even
+ * if the server is back on.
+ */
+void MQTTClient::onConnectTimeout(void)
+{
+	switch (state()) {
+	case Connecting:
+		qDebug() << "force to disconnect";
+		disconnectFromHost();
+		/* fall through */
+	case Disconnected:
+		qDebug() << "re-try do connect";
+		connectToHost();
+		break;
+	case Connected:
+		break;
+	}
+}
+
 void MQTTClient::onStateChanged(ClientState state)
 {
-	qDebug() << "mqtt state " << state;
+	qDebug() << "mqtt state: ";
+
 	switch (state) {
-	case Disconnected: break;
-	case Connecting: break;
-	case Connected: break;
-	default: break;
+	case Disconnected:
+		qDebug() << "disconnected";
+		break;
+	case Connecting:
+		qDebug() << "Connecting";
+		break;
+	case Connected:
+		qDebug() << "Connected";
+		break;
 	}
 }
 
@@ -68,7 +99,7 @@ void MQTTClient::onError(ClientError error)
 
 void MQTTClient::onConnected()
 {
-	qDebug() << "connected";
+	qDebug() << "subscribe";
 	this->subscribe(QString("sensors/#"), 1);
 }
 
@@ -151,7 +182,6 @@ void MQTTClient::allHeatersOn(bool on) {
 		for (int j = 0; j < r->heaters.count(); j++) {
 			const struct Heater *h = &(r->heaters.at(j));
 
-			/* TODO: check if connected */
 			publish_msg(h->ctrl_topic, payload);
 		}
 	}