93. How to search all the MQTT topics in the HMI?

If HMI is a MQTT publisher, how can the subscriber know what are the topics in it? When the HMI connects with the broker for the first time (It can be HMI or third party device.), it will send an initial topic with MQTT information in project file. The subscriber can then subscribe to this topic to get all the topics in the HMI.

Step 1. Subscribe the following topic: 
iot-2/type/mt/id//evt/topics_update/fmt/json
The is the [Registration ID] used in MQTT setting of HMI project. Or use “+” replacing in order to subscribe to all HMIs at the same time.
Use MQTT.fx as the subscriber example:

Step 2. By subscribing this topic, the subscriber will receive the following text message: