Every other year, I'm part of an international project with students from the US and Germany. The students usually use Arduinos to automate a smart house. Their main assignments deal with programming an elevator, a photovoltaic system or heating a pool etc. One of the group writes an app to control all the systems.
This year, we provided all the groups with a mqtt backend and I prepared some boards to make accessing the mqtt server as easy as sending serial messages.
Details on how to use the boards are in my lecture notes attached.
Possible serial commands:
time: get current time (example answer: Time:13:34:53)
+topic: (e.g. “+test/topic”), subscribes to new topic
-topic: end subscription
[Topic][Message]: publish a message (no subscription