Issue in adding message properties in paho MQTT publish method

Athira Gopinath(UST,IN) 121 Reputation points
2023-04-11T10:21:35.9+00:00

Hi, As part of our work, we need to apply routing queries to the payload receives at IoTHub via MQTT protocol. For that purpose, the properties of payload should be as {'content-encoding': 'utf-8','content_type':'application/json'}. So that we have applied these properties to this payload Payload:{"datetime": "2023-03-30 06:20:30","RaR": 123, "level": 750, "id": "1234"}. Attaching the code snippet.

final_payload={"datetime": "2023-03-30 06:20:30","RaR": 123, "level": 750, "id": "1234"}
publish_properties = props.Properties(PacketTypes.CONNECT)
publish_properties.UserProperty = ("application/json","3")
publish_properties.UserProperty = ("content_encoding", "UTF-8")
client.publish(topic, payload=final_payload, qos=1,properties=publish_properties)

But the properties are not getting applied on the payload. It is not getting filtered out. Please suggest some solution to resolve this issue. Thanks Athira

Azure IoT Hub
Azure IoT Hub

An Azure service that enables bidirectional communication between internet of things (IoT) devices and applications.

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  2. Aaron Morris 0 Reputation points
    2025-09-07T22:16:46.49+00:00

    This may be tangential to the overall problem, but the reason the MQTT User Properties are not being sent in the original code is because Python paho.mqtt defaults to MQTTv311 (and the code explicitly connects with this protocol above).

    In order to use UserProperties, you must connect with MQTTv5.

    client = mqtt.Client(client_id=device_id, protocol=mqtt.MQTTv5)

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  3. Sedat SALMAN 14,385 Reputation points MVP
    2023-04-11T11:48:52.9+00:00

    Check the document for user properties [http://docs.oasis-open.org/mqtt/mqtt/v5.0/cs02/mqtt-v5.0-cs02.html#_Toc514345337] you can use the following 

    import paho.mqtt.client as mqtt
import paho.mqtt.properties as props
from paho.mqtt.packettypes import PacketTypes

final_payload = '{"datetime": "2023-03-30 06:20:30", "RaR": 123, "level": 750, "id": "1234"}'
topic = "your_topic_here"

# Your MQTT client connection code here

publish_properties = props.Properties(PacketTypes.PUBLISH)
publish_properties.UserProperty = ("Content-Type", "application/json")
publish_properties.UserProperty = ("content-encoding", "UTF-8")

client.publish(topic, payload=final_payload, qos=1, properties=publish_properties)

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