NO read what you suggested and what was found to work
there is a subtle difference
“/0/”
Richard
Why dont you just call me a liar n???
as thats what you are saying, and my character set is UTF-8
I find that very insulting, as I think others reading this thread will intepret as well
Richard
I didn’t call you a damn thing. I answered someone else’s question. Calm your tits and reign in those feels, buddy.
Perhaps others reading the thread, if they waste that much time, won’t be so quick to not follow the conversation and who is replying to whom.
I’m not even sure where the “/set” part of the topic even came from. The posted screenshot only shows it ending with the “/0” part.
What made you try to use that entire topic in the first place?
Hi
I spotted it in the topics listed in the LH pane on MQTT-explorer,
/iot4//relay/set
it was only there once, but it didn’t fit in with the rest of status reports etc.
Just thought I’d try all combinations of hostname with that and number, just got lucky being too lazy to type the full topic name hence copy and paste.
I did hear back from Robi, who sells them, but hes moved over to domoticz, from odd bits I’ve found on line, it cound be Spanish s/w in it. But the site it might come from is password protected, so I couldn’t get any further.
I had my share of problems with the IOT4SH02RELAY MQTT. Its documentation is completely inaccurate. When you publish into relay-control addresses, the relay state topic doesn’t change!
Confirmed this using MQTT Explorer and device web-GUI. So, if you want HA to bve aware of staes, you need to manually change both the state and relay state?! 
This device is completely impossible to debug without MQTT Explorer or similar tools.