Zigbee two way communication

I’m quite new to Openhab and still figuring out how to setup certain things.

I have setup the ZigBee binding to work with a CC2531 dongle. I am able to control a Ikea tradfri Light bulb without problems. The reason I want to use zigbee over, for example, RF433 controlled devices is that ZigBee supports two way communication. I would expect that if I try to switch on the light when it is disconnected from the mains a warning is given that the device is offline.

From the Paper UI the lightbulb indicates online even if it is not powered at all.

This also triggers a more generic question… How can I configure Openhab that my other items, like temperature sensors, are checked if they are still online.

Not unless you write some Rules to do this.

I haven’t used Zigbee much but I suspect that it won’t appear as offline until it has been off for long enough for at least one polling period to pass.

Search the forum and you will see how you can trigger a Rule when a Thing goes offline which you can set to an Item that gets checked and so on. But this will need to be implemented in Rules.

See Design Patterns: Generic Is Alive (NOTE I just updated this article significantly).

The problem is that the Thing does not go offline at all when I disconnect it from the mains. The same holds for the zigbee coordinator (CC2531EMK Coordinator). When I pull out the USB dongle the Thing status remains online. To me this seems more a problem in the binding. Is there a specific catagory in the forum when I can address this issue?
Related to this polling cycle… how long is this by default? Can I set this to a specific value?

Great article, thanks! I got the expire binding to work for checking if my MQTT sensors are still online.