Read MQTT topic at app start

Hi Qts!

The tasks is this – when I start my program, at first I have to read a topic from some MQTT broker for some information. Before QT I made programs using Paho MQTT, and I used a synchronous reading mode, the functions like this:

rc = MQTTClient_receive(mqtt_client, &topic_received, &topic_received_len, &message_received, 1000);

I use QMQTT now; as far I understand it has only asynchronous reading (with a callback). But I need to read an MQTT topic right on the app start.