mqtt 5.0 Request Response using emqtt library. How set Properties?

[cocoaway]

No description provided.

[cocoaway]

Hello,
I'm trying to make a request/response publish but is not clear how set Response topic and Correlation data in
:emqtt.publish(Client, Topic, Properties, Payload, PubOpts)

Can you provide how set Properties ?

Thx.

Luca

[emiltin]

Did you find an answer to this? I'm also wondering how to set the response topic.

[qzhuyan]

just set in Properties map, take a look in emqtt_props.erl.

[emiltin]

Thank you. Right, I can set 'Response-Topic' to a string, and I now see this logged when I publish:

[debug] [clientid: "emqtt-ab49cf24b912acf684db", msg: ~c"SEND_Data", packet: {:mqtt_packet, {:mqtt_packet_header, 3, false, 1, false}, {:mqtt_packet_publish, "command/tlc_582a/plan", 14, %{"Response-Topic": "response/tlc_582a"}}, "7"}, socket: #Port<0.30>]

But when another client receives this I don't see any properties:

%{
  client_pid: #PID<0.189.0>,
  dup: false,
  packet_id: 1,
  payload: "7",
  properties: %{},
  qos: 1,
  retain: false,
  topic: "command/tlc_582a/plan",
  via: #Port<0.12>
}

Shouldn't I see the Response-Topic as a property when I receive the message? Or is there another way to get it?

Note: I'm using Elixir.

[thalesmg]

Did you connect using MQTT protocol version 5?

{:ok, c} = :emqtt.start_link(proto_ver: :v5, ...)

[emiltin]

Great tip! I thought I did, but realized I only did so in one of the clients, not the other. Now it works 👍