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IOT3: Connecting to the MQTT and publishing data
In the following scenario, you will learn how to connect to the MQTT broker and publish a message.
Prerequisites
To implement this scenario, it is necessary to get familiar with at least one of the following scenarios first:
and obligatory:
[pczekalski]Tu trzeba dodać bibliotekę do MQTT, pewnie pub-sub client
Suggested Readings and Knowledge Resources
Hands-on Lab Scenario
Task to be implemented
Connect to the “internal IoT” WiFI access point as presented in the scenario IOT2: Reading IP address of the WiFi—present connection status on the display (for tracing). Once connected to the networking layer, connect to the MQTT broker and present the connection status on the display, then publish an MQTT message.
MQTT clients are identified by their name, so use a unique one, e.g., the end of the IP address assigned, your unique name, etc. It is essential because if you accidentally use someone else's name then you will mess with messages, and your MQTT client will be instantly disconnected when another one with the same name connects!
Start
Check if you can clearly see a full display (of your choice) in your video stream. Book a device and create a dummy Arduino file with void setup()… and void loop()….
Implement a connection to the “internal IoT” network as a client. Refer to the supervisor or the technical documentation on credentials (SSID, passphrase). We do not provide the exact code on how to connect to the WiFi as it is a part of IOT2: Reading IP address of the WiFi scenario.
Steps
Step 1
Include
Result validation
You should be able to connect to the WiFi and present the dynamically assigned IP address by the DHCP server.
Note that due to the dynamic nature of the lab, IP addresses can change both during connection (on lease refresh) or between consecutive connects.
FAQ
My MQTT client disconnects randomly: The most common reason is you're using a non-unique MQTT client name. Please change it to some other (even random generated) and give it another try.
How do I observe messages that I send?: Use a software client, such as MQTT Explorer, if you're able to access the “internal IoT” network (you're in the range of the network). If you're remote, the only way is to book another device and implement a client subscribing to your message. Our MQTT broker is also visible in the campus network on the wired interfaces so that you can access it, e.g. via EduVPN or from the laboratory computers. Refer to the supervisor for IP and credentials.
Do I need to authorise to publish and subscribe?: Yes, you do. The supervisor provides the user and password on demand, also presented in the Node's technical documentation.
