Sending Messages & Commands to Your Raspberry Pi Using MQTT

In this tutorial learn how to send messages to/from your local computer to your Raspberry Pi over the local network using the Mosquitto MQTT and Python! It's free and incredibly easy to set up and manage. This can form the basis of incredible IoT and distributed systems applications! You can do some amazing things with this simple tool in practice.

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An interactive version of this video and downloadable instructions available on Razzl on the App Store and Android Store which contains the code and PDF instructions. Cheers!

IOS: https://apps.apple.com/us/app/razzl-watch-make-learn/id1604713309

Step 1-) Raspberry Pi Setup

We need to setup the broker installation the Raspberry Pi, there are a view installation steps below followed by code.

On your Raspberry Pi run the following commands in your terminal.

• sudo apt update
• sudo apt install -y mosquitto mosquitto-clients
• pip install paho-mqtt

Next, add these two lines to the config

• listener 1883
• allow_anonymous true

Add them to the bottom of the file by first typing

• sudo nano /etc/mosquitto/mosquitto.conf

You should then restart the mosquitto service with the command,

• sudo systemctl restart mosquitto

The last information you need is the IP Address of your Raspberry Pi, you can get it by running the 'ifconfig' command in the terminal and looking at the following section (See Image). In the wlan0 section.

Now you have all of the infrastructure you need on the Raspberry Pi side to use Mosquitto!

The only thing left is to download and run the code in Python attached to this project on Razzl, or simply copy the code in the video.

You should run the code once and let it remain running as long as you want to receive messages on the Pi, you can modify the on_message function to fit the demands of your project, this is the function that is called every time your MQTT channel receives a message.

Your Raspberry Pi at this point is waiting for messages/commands, very exciting. You should also get a result code of 0 when you first run the script. That means the code is working.

Step 2-) Local Code

On your local computer run the following code, attached to the project on Razzl. It is very simple, you are just sending a message to the topic for the MQTT broker.

Make sure you also pip install paho.mqtt

If everything is successful you should see a message in the console of your Raspberry Pi Python code as shown in the image! Congrats you did it.

You can now leverage MQTT and do more intricate things, such as send commands to control GPIO pins, maybe send a command to take a photo or more! This can form the basis of incredibly complex and powerful IoT and embedded systems applications.

Conclusion

Hope you enjoyed the video, let me know what you think of the Razzl platform. Be sure to follow me there and also follow me on YouTube and other social media. Also, would love to hear your questions in general and I look forward to doing more intricate MQTT and robotics tutorials for you guys.