MQTT and Cayenne

Introduction

myDevices Cayenne claims to be the world's first drag and drop IoT builder. It provides a dash board on which the user can set up predefined widgets in which sensor data can be displayed or from which actuators can be controlled. It also allows to trigger actions when certain values appear on the sensors read out. For example, a ventilator can be switch on when the values read from a thermometer reach a certain limit. Cayenne uses MQTT a simple subscribe-publish protocol running on top of TCP.

MQTT

MQTT (Message Queuing Telemetry Transport: a publish-subscribe based message protocol running of top of TCP. A broker takes subscriptions for messages of a certain “topic” and it sends messages, coming from publishers to everyone having subscribed to the topic.

We can easily test the mechanism using the mosquitto MQTT broker. Install mosquitto and mosquitto-clients using apt. mosquitto is the broker and mosquitto_sub allows you to subscribe to a topic while mosquitto_pub will publish a topic.

-- Uli Raich - 2020-08-31

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