I’m in the process of figuring out the Chirpstack architecture and flow. I wrote a couple of Rust tools to list devices and enqueue messages. At first, I assumed I would see the enqueue messages passed to the MQTT broker but this turned out to be wrong. Looking at some diagrams on the NET, I noticed gRPC rquests seem to parallel the MQTT process. The only way for me to see the entire flow is to code a device simulator and submit a message. gRPC requests appear to be mainly administrative and diagnostic??? Is this correct? Thank you.
You are likely subscribed to the incorrect MQTT topic. The only connection between Chirpstack and the gateway is the MQTT broker, so a downlink request must go through it. If you subscribe to “#” you should see the downlink requests under a topic like "<region_prefix>/gateway/<gateway_eui>/command/down