Hi,
I have been having problems setting up using MQTT. I wanted to check all messages that came through the MQTT broker. While trying the log on the Raspberry and testing this and that, I stumbled over a nice app on my phone which showed me all messages so I could figure out the syntax to use.

My story:
I followed the Sonoff tutorial from Tasmota Wiki to get the Sonoff Basic to run MQTT and to get MQTT running on a Raspberry Pi 3b.
That worked I think; I got the response that showed like in the test by Ruiz.
While on the esp32 course doing the esp32/temperature project MQTT worked fine, the Sonoff Basic didn’t respond.
The website from the sonoff worked fine; it responded to the on/off there.
So it had to be in the settings for the Sonoff or the syntax I used.

If only I could see all the MQTT messages going in and out the broker.

The app that did this for me is called “Iot MQTT Panel” by Rahul Kundu.(you do not have to buy it to use it.)

After setting up the server info, and connecting to it, make a panel by pressing the + icon and select ‘Text log’.
Add any Panel Name you like.

As topic you use a single ‘#’ (without the quotes). Qos can be on 0.
at Additional Options you can set timestamping on or off, set the size of the log screen (5 lines and 5 persistence works for me)
Click Save!

And there you see all MQTT messages.