Improve MQTT disconnection handling

hc2mqtt

@@ -48,6 +48,10 @@ def hc2mqtt(
         elif rc == 0:
             print(now(), f"MQTT connection established: {rc}")
             client.publish(f"{mqtt_prefix}LWT", payload="Online", qos=0, retain=True)
+            for device in devices:
+                mqtt_set_topic = f"{mqtt_prefix}{device['name']}/set"
+                print(now(), device["name"], f"set topic: {mqtt_set_topic}")
+                client.subscribe(mqtt_set_topic)
         else:
             print(now(), f"ERROR MQTT connection failed: {rc}")
 
@@ -119,6 +123,7 @@ def client_connect(client, device, mqtt_topic):
 
     host = device["host"]
     device_topics = topics
+    client.on_message = on_message
 
     for value in device["features"]:
         if (
@@ -136,10 +141,6 @@ def client_connect(client, device, mqtt_topic):
         if not topic.isdigit():  # We only want the named topics
             state[device_topics[topic]] = None
 
-    mqtt_set_topic = mqtt_topic + "/set"
-    print(now(), device["name"], f"set topic: {mqtt_set_topic}")
-    client.subscribe(mqtt_set_topic)
-    client.on_message = on_message
 
     while True:
         try:
@@ -175,12 +176,15 @@ def client_connect(client, device, mqtt_topic):
                 if not update:
                     continue
 
+                if client.is_connected():
                     msg = json.dumps(state)
                     print(now(), device["name"], f"publish to {mqtt_topic} with {msg}")
                     client.publish(mqtt_topic + "/state", msg)
+                else:
+                    raise Exception("Unable to publish update as mqtt is not connected.")
 
         except Exception as e:
-            print("ERROR", host, e, file=sys.stderr)
+            print("ERROR", device["name"], e, file=sys.stderr)
 
         time.sleep(5)