This is an old revision of the document!
Table of Contents
U3: Sending MQTT messages
In this scenario, you will send MQTT message exposing temperature and humidity to the MQTT server available on the internal.IOT network. By sending sensor data you will learn, how to expose the device's state and how to inform others that your device stopped working uncontrolled way.
Target group
Undergraduate / Bachelor / Engineering Students
Prerequisites
We assume you already know, how to:
- handle DHT sensor to read temperature and humidity,
- handle LCD screen to present information,
- connect to the existing WiFi network:
internal.IOT, - additionally we will ask you to install and use an MQTT client of your choice. We suggest using MQTT Spy, but any MQTT client that will let you subscribe to the MQTT messages is OK. You connect it to the public IP of the MQTT broker (see below).
MQTT broker present in the internal.IOT network is also visible under public address. So whenever you publish an MQTT message using VREL node that is connected to the internal.IOT network, you may subscribe to it using other devices connected to the internal.IOT i.e. other VREL node or if you're physically present at SUT in the IOT laboratory room 320, then you can connect your mobile and laptop to the internal.IOT network and use “internal” IP address. However, if you're in a remote location you can access the same broker under public IP as stated in the node description. Same messages published on the internal network are also visible on the public side. Mind, to access MQTT broker you need to use IP, user and password (applies to both public and private IPs of the MQTT Broker). Refer to the node documentation for the latest information.
Note - information present in source code samples can be not up-to-date - remember to refer to the VREL node documentation for the latest information on IPs, users and passwords for both
internal.IOT network access and for the MQTT Broker.
Scenario
In this scenario, you will connect to the
Result
Describe expected result when scenario is finished.
Start
Write starting conditions, i.e. what to do at the beginning, what to pay attention before beginning, how the mechanical part should look like, etc.
Steps
Write some extra information if i.e. some steps are optional otherwise cancel this paragraph (but do not remove header).
Step 1
Describe activities done in Step 1.
…
Step n
Describe activities done in Step n.
Result validation
Provide some result validation methods, for self assesment.
FAQ
This section is to be extended as new questions appear.
When using the printed version of this manual please refer to the latest online version of this document to obtain the valid and up-to-date list of the FAQ.
Provide some FAQs in the following form:
Question?: Answer.
