Is the TRB142 gateway capable of performing the following tasks:
1. TRB142 does have an MQTT broker and publisher feature, you can read more about MQTT configuration in TRB142: https://wiki.teltonika-networks.com/view/TRB142_MQTT
2. RS232 data can be sent using Data to server feature that is available in TRB142. Data to server supports HTTP and MQTT protocols. More about configuration: https://wiki.teltonika-networks.com/view/TRB142_Data_to_Server
3. Answered on the first point. When you configure TRB142 as a broker it can subscribe to specific topics.
4. Unfortunately, data cannot be sent using MQTT to a device connected via RS232 to TRB142.