Descriptive part
Middleware for IoT is a subject that allows us to discover the basics of communications between machines with two protocols used worldwide, ONEM2M and MQTT and finally the processing of this information via node-red.
It allowed us to master these 3 technologies that we then use in our innovative project. It is thus organized in 3 practical works: ONEM2M, MQTT and node-red, which I will detail quickly via examples. For a more detailed definition of terms and achievements, I invite you to read the reports.
TP n°1:
OneM2M
With OneM2M, we need to create AE resources using HTTP request or a client. We fully set access rights to the right users and then fully describe the application.
Classical use of OneM2M standard
Using a POST request, we push data to the application called Smart_Meter. Here, 230V.
This is the view in the OM2M interface where we can see informations about the application.
Here, we have the application's descriptor fully specified.
Here, we have the application's data container example with 600 lux pushed.
MQTT, for "Message Queuing Telemetry Transport", is an open source messaging protocol that provides non-permanent communications between devices through the transport of their messages. It is based on a system of publication and subscription via a broker.
How MQTT usually works
Here is an example of the use of MQTT for our innovative project. We have a broker running on a Raspberry PI on port 1883 and on a different network. It only allows connections from known users with a username/password pair on port 1883. It acts as a relay between the publisher and the subscriber.
Here is the view of the broker during the publication of V2X messages published on the topic "platooning/cam/master_car".
These messages are then retrieved by the slave vehicle that has subscribed to the same topic as before. It then decodes the information it needs.
TP n°2:
MQTT
TP n°3:
node-red
Node-RED is a programming tool for wiring together hardware devices, APIs and online services in new and interesting ways. It provides a browser-based editor that makes it easy to wire together flows using the wide range of nodes in the palette that can be deployed to its runtime in a single-click.
Here is a simple example of a node-red flow. Basically, we get the last luminosity value from the Application Entity luminosity_sensor. Then, this value is published on the "middleware" topic via MQTT. On the top of the flow, we have the possibility to send the value 50 or 700 to the AE. As a simulation, we subscribe on the same flow to the topic "middleware" and according to a threshold we switch on or off a simulated actuator.
The flow above allows you to retrieve real-time temperature, humidity and CO2 values from a Netatmo station. Those informations are then displayed on a dashboard.
Information displayed on the dashboard. The graphs are flat because the capture was only run for example purposes for a very short time.