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Managing MQTT subscriptions Examples

Table of contents

Topics

To subscribe to messages of a specific device, a combination of baseTopic and a device topic must be used. Reference to image below. The baseTopic can be fetched from netFIELD-API (View examples or swagger of API).

The following diagram represents the workflow and structure of topics inside the netFIELD-Data-Service system.

Topic behaviour

To subscribe to a topic and start receiving its messages, you can do that from the netFIELD platform or locally on the device using the netFIELD App Platform Connector.

netFIELD App Platform Connector - subscribe to receive messages from device

Subscribe to Topics in netfield platform 1

Subscribe to Topics in netfield platform 2

Subscribe to Topics in netfield platform 3

Examples

General information

Provided examples connect to the device local MQTT broker, subscribe a topic to receive its messages, and publish a user message on a topic.

The following sequence diagrm illustrates performed interactions:

MQTT Sequencediagram

C#

MQTTnet is used as library to connect to a broker via MQTT to receive and publish messages.

Javascript

MQTT.js is used to connect to broker to receive and publish messages.

Python

Eclipse Paho client library for MQTT Broker connection to receive and publish messages. https://www.eclipse.org/paho/index.php?page=clients/python/index.php

Troubleshooting

MQTT client disconnects (imediately).

Multiple possible issues:

  • Subscriptions are performed, that are not permitted.
  • TLS is not used.
  • Publishes to the broker are performed that are not permitted.