How a device can publish data using MQTT only?

[Charly86 (Charles)]

Interesting, I saw multi users

MQTT Multi user

Great to be able to have multiusers Just asking, what about an easier solution using as HTTP the existing user API key and post to topic something like that? prefix/user_api_key/node/ or prefix/api/user_api_key/node/

but rather more complicated on server side than using user api key in topic