Reset relays on MQTT disconnection

With option #define MQTT_DISCONNECT_RELAY_DEFAULT set to 1, all relays
will be reset in case of MQTT disconnection to avoid a connected device
being switched on while MQTT is not under broker control any more.

code/espurna/config/general.h

@@ -513,6 +513,8 @@ PROGMEM const char* const custom_reset_string[] = {
 #define MQTT_USE_JSON_DELAY         100             // Wait this many ms before grouping messages
 #define MQTT_QUEUE_MAX_SIZE         10              // Size of the MQTT queue when MQTT_USE_JSON is enabled
 
+#define MQTT_DISCONNECT_RELAY_DEFAULT   1           // 0 - do nothing, 1 - reset relays to OFF in case of MQTT disconnection
+
 // These are the properties that will be sent when useJson is true
 #ifndef MQTT_ENQUEUE_IP
 #define MQTT_ENQUEUE_IP             1

code/espurna/relay.ino

@@ -654,6 +654,17 @@ void relayMQTTCallback(unsigned int type, const char * topic, const char * paylo
 
     }
 
+    if (type == MQTT_DISCONNECT_EVENT)
+    {
+        if (MQTT_DISCONNECT_RELAY_DEFAULT == 1){
+            for (unsigned int i=0; i < _relays.size(); i++){
+                DEBUG_MSG_P(PSTR("[RELAY] Reset relay (%d) due to MQTT disconnection\n"), i);
+                relayStatusWrap(i, false, false);
+            }
+        }
+
+    }
+
 }
 
 void relaySetupMQTT() {