Regarding MQTT broker topics for uplink and downlink

[harsha]

Hi,

I was able to configure MQTT integration and receive uplinks on topic format “application/[ApplicationID]/device/[DevEUI]/event/up” and scedule downlink on “application/[ApplicationID]/device/[DevEUI]/command/down”.

Is there any way I can change the topics to something else like say get uplink on a topic called “AllMyUplinks” and send downlink to a device on “MyDownlink”.

The following article mentions “The default topic for scheduling downlink payloads is:”. So I was wondering is it possible to change topics which is deifferent from “Default”

MQTT - ChirpStack open-source LoRaWAN® Network Server

Regards,
Harsha

[martin]

Hi, in V3 you could originally use separete topic tepmplates for each message type, later changed to event style topics. So you could do this for example:

 # MQTT integration backend.
 [application_server.integration.mqtt]
  uplink_topic_template="application/{{ .ApplicationID }}/device/{{ .DevEUI }}/rx"
  downlink_topic_template="application/{{ .ApplicationID }}/device/{{ .DevEUI }}/tx"
  join_topic_template="application/{{ .ApplicationID }}/device/{{ .DevEUI }}/join"
  ack_topic_template="application/{{ .ApplicationID }}/device/{{ .DevEUI }}/ack"
  error_topic_template="application/{{ .ApplicationID }}/device/{{ .DevEUI }}/error"
  status_topic_template="application/{{ .ApplicationID }}/device/{{ .DevEUI }}/status"
  location_topic_template="application/{{ .ApplicationID }}/device/{{ .DevEUI }}/location"

I wouldn’t expect this to work in V4 tho.

[harsha]

Hi Martin,

Thank you.

So I am assuming the topics would still need the applicationID and Device EUI to route messages. My earlier question was if we gave a random topic name like “AllMyUplinks” to receive uplinks from devices and send downlink to a device on topic “MyDownlink” - without providing the application ID or device id anywhere in the topic.

I am using Chirpstack v4 deployed with docker compose.

chirpstack:
    image: chirpstack/chirpstack:4.0.4

  chirpstack-gateway-bridge-eu868:
    image: chirpstack/chirpstack-gateway-bridge:4.0.1

  chirpstack-rest-api:
    image: chirpstack/chirpstack-rest-api:4.0.4

Regards,
Harsha

[martin]

Oh ok, I was thinking more like: uplink_topic_template="application/{{ .ApplicationID }}/device/{{ .DevEUI }}/allmyuplinks".

You could propbably do what you want with some mqtt magic, but usualy you just subscribe to application/+/device/+/event/up in your app and that will give you all the uplinks too.

So I am assuming the topics would still need the applicationID and Device EUI to route messages.

Well, there was originally note saying Note: the downlink_topic_template must contain both the application id and # DevEUI substitution!, so you could try, but personally I would rather use the default route.