What's the use in passing an argument if you don't use it?

boil_kettle/mqtt.ino

@@ -45,7 +45,7 @@ void SetupMQTT(String broker) {
   // Note: Local domain names (e.g. "Computer.local" on OSX) are not supported
   // by Arduino. You need to set the IP address directly.
   Serial.println("Setup MQTT client.");
-  mqtt_client.begin("192.168.1.198", net);
+  mqtt_client.begin(broker, net);
   mqtt_client.onMessage(MessageReceived);
 
   ConnectMQTT();