OpenHab and MQTT

Well, the first part of that was easier than I was expecting..

I installed OpenHab on my PC – told it about my MQTT broker…  which I’m calling “petebroker”

Added in these three lines from an example…


I used the openhab demo as I’ve never used the package before…

If I use a separate mqtt client (MQTT-SPY) subscribed to


For example.. I can see the ON and OFF commands from OpenHab – so clearly the MQTT is working. All the commands in the demo are producing MQTT messages..


But – I haven’t the FOGGIEST idea of what topic and message to send BACK to Openhab to, say activate the little indicator  on the bathroom mirror icon. I’ve tried combinations such as


and the message ON -  nothing – zilch. Can anyone put me out of my misery.

Oh just to prove it worked – I set my little ESP-12 up to subscribe to the bathroom mirror – and toggle GPIO2 accordingly – and it worked straight away!!! No problem – stick a relay on there and we’re in business (JUSt had delivery of a couple of solid state relays which claim to work from 3v upwards and control 2amps at 250v)  – but I really need to understand information in the other direction. Any Openhab wizards out there?