Use Gateway Bridge to Send Data to Gateway Directly over MQTT

Is it possible to send data directly to the gateway over MQTT or any other means via gateway bridge?

According to the architecture diagram, network-server uses MQTT to communicate with the gateway bridge which then sends the data to the gateway (Laird). However, when I watch the gateway/id/commands/+ topic, I don’t see any data. How does network server communicate with the gateways?

I assume it is just as simple as publishing to gateway/id/command/down to schedule a downlink?

There is a lot to see if you watch all gateway topics (gateway/#):

Note that by default it is in protobuf format (compact, faster), so you may want to switch gateway and NS to JSON if you want something human-readable for perusing.

I assumed that I would see all downlink sent by the network server if I watched the gateway/{{ }}/command/down topic, but that topic appears empty. I get plenty of data on all of the other gateway topics, including config, but nothing on down.