mosquitto - How to discover all devices in MQTT-enabled LAN?

Question

In my LAN there are several MQTT-enabled devices (Tasmota) and I am writing an MQTT client (Javascript, through mosquitto websocket and PAHO client library).

Which is the best way to discover all online devices in the LAN and their corresponding device name? I thought using the LWT message that every device sends, but I don't know how to subscribe to all LWT message from unknown devices.

The LWT "Online" messages are coming through with this path: tele/<device_name>/LWT, but I don't want to subscribe to ALL "tele" messages, as they are too many.

Answer 1

You can use single level wildcard topics.

e.g.

tele/+/LWT

This will get you all the topics that start with tele and end with LWT with only on element in the middle.