This post will also be very short (or so I hope).
Setting up MQTT in your Keil MDK project is very easy especially for the Eclipse Paho client for C. I did this in one git commit. You will notice that of the three flavors available, I chose the MQTTPacket because it is lightweight. The other flavors required some more work. Setting the timing parts for the MQTTClient, required understanding the library perfectly to work it out. One requires the timing to work if you need to subscribe to a topic or if you need the broker to confirm delivery (QoS 2 or QoS 1). For the basic proof of concept, QoS 1 works fine. It means I need no response from the broker.