In this guide I will show you a quick, easy an pretty straight-forward way to install Mosquitto and Node-RED onto a Raspberry Pi running Raspberry Pi OS.

Install Mosquitto MQTT-broker

sudo apt install -y mosquitto mosquitto-clients
sudo vim /etc/mosquitto/mosquitto.conf

Add following lines at end:

listener 1883
allow_anonymous true

Enable and start mosquitto

sudo systemctl enable --now mosquitto

Test receiving of MQTT-messages

mosquitto_sub -d -t testTopic

Install Node-RED

On your Raspberry open a terminal and enter following lines to download and install Node-RED

bash <(curl -sL https://raw.githubusercontent.com/node-red/linux-installers/master/deb/update-nodejs-and-nodered)

Now we need to enable and start Node-RED

sudo systemctl enable --now nodered

Install Node-RED dashboard

node-red-stop
cd ~/.node-red
npm install node-red-dashboard

Now we test to access Node-RED from another machine on the same network by opening a web-browser and access following URL:

http://[RasperryPi_IP]:1880

Whether you cannot access your Node-RED dashboard most likely your firewall is blocking to access it remotely. So we install and configure the Ubuntu firewall-tool ufw

sudo apt install ufw
ufw allow 1880
ufw allow 1883
sudo ufw enable

Configure Node-RED

You should now be up and running and able to add an mqtt-in node via your Node-RED dashboard and configure your MQTT-broker with URL 127.0.0.1:1883