How to Install Mosquitto MQTT Broker on Ubuntu and Raspberry Pi
Introduction
Before IoT devices can exchange messages using MQTT, they need an MQTT broker. The broker acts as the central communication hub, receiving messages from publishers and delivering them to subscribers.
One of the most popular MQTT brokers available today is Eclipse Mosquitto. It is lightweight, open-source, easy to install, and widely used in IoT projects ranging from smart homes and environmental monitoring systems to industrial automation.
In this tutorial, you’ll learn how to install Mosquitto MQTT Broker on Ubuntu and Raspberry Pi, verify the installation, and test MQTT communication using the built-in command-line tools.
By the end of this guide, you’ll have a fully functional MQTT broker ready to connect ESP32 devices, Node-RED dashboards, and other MQTT clients.
What is Mosquitto?
Mosquitto is an open-source MQTT broker developed by the Eclipse Foundation.
It supports:
- MQTT v3.1
- MQTT v3.1.1
- MQTT v5.0
Mosquitto is popular because it:
- Requires minimal system resources
- Runs efficiently on Raspberry Pi
- Supports Linux, Windows, and macOS
- Supports TLS encryption
- Supports authentication and access control
- Is free and open source
Why Use Mosquitto?
Mosquitto is one of the most widely used MQTT brokers in IoT development because it is reliable, lightweight, and simple to configure.
Common use cases include:
- Smart home automation
- ESP32 and Arduino projects
- Node-RED dashboards
- Industrial monitoring systems
- Environmental data collection
- Agricultural IoT applications
Because it requires very little processing power and memory, Mosquitto performs exceptionally well on Raspberry Pi devices.
Prerequisites
Before starting, ensure you have:
- Ubuntu 20.04 or later
- Raspberry Pi OS
- Internet connection
- Terminal access
- User account with sudo privileges
Update Your System
Before installing Mosquitto, update your package list and installed packages.
sudo apt update sudo apt upgrade -y
This ensures your system is running the latest software versions.
Install Mosquitto MQTT Broker
Install Mosquitto and its client utilities using the package manager.
sudo apt install mosquitto mosquitto-clients -y
The installation includes:
Mosquitto Broker
The MQTT server responsible for receiving and routing messages between MQTT clients.
Mosquitto Clients
Command-line tools used for testing MQTT communication.
Useful tools include:
- mosquitto_pub
- mosquitto_sub
Enable Mosquitto Service
Configure Mosquitto to start automatically during system boot.
sudo systemctl enable mosquitto
Start the service.
sudo systemctl start mosquitto
Verify the service status.
sudo systemctl status mosquitto
Expected output:
Active: active (running)
If you see this message, the broker is running successfully.
Verify Mosquitto Installation
Check the installed Mosquitto version.
mosquitto -h
Example output:
mosquitto version 2.x
This confirms that Mosquitto is installed correctly.
Test MQTT Communication
Let’s verify that the broker can receive and deliver messages.
Open Terminal 1 and subscribe to a topic.
mosquitto_sub -h localhost -t test/topic
Open Terminal 2 and publish a message.
mosquitto_pub -h localhost -t test/topic -m "Hello MQTT"
If everything is working correctly, Terminal 1 should display:
Hello MQTT
Congratulations! Your MQTT broker is successfully routing messages.
Understanding the Test
The MQTT communication test involves three components.
Publisher
mosquitto_pub
Sends messages to the broker.
Broker
Mosquitto
Receives and routes messages.
Subscriber
mosquitto_sub
Receives messages from subscribed topics.
This demonstrates the publish-subscribe architecture that makes MQTT efficient for IoT applications.
Allow Remote MQTT Connections (Development Setup)
For local testing and learning purposes, you may want devices on your network to connect to the broker.
Open the Mosquitto configuration file.
sudo nano /etc/mosquitto/mosquitto.conf
Add the following lines:
listener 1883 allow_anonymous true
Save the file and restart Mosquitto.
sudo systemctl restart mosquitto
Important
The allow_anonymous true setting should only be used in local development environments.
For production deployments, enable authentication and TLS encryption.
Continue with: MQTT Security with TLS
Find Your MQTT Broker IP Address
To allow other devices to connect, determine your system’s IP address.
hostname -I
Example output:
192.168.1.100
Other devices on the network can connect using:
192.168.1.100:1883
Port 1883 is the default MQTT port.
Check Open Port
Verify that Mosquitto is listening on port 1883.
sudo netstat -tulpn | grep 1883
Expected output:
tcp 0 0 0.0.0.0:1883
This confirms the broker is accepting connections.
Basic Mosquitto Configuration
The main configuration file is located at:
/etc/mosquitto/mosquitto.conf
Additional configuration files are stored in:
/etc/mosquitto/conf.d/
View the default configuration:
sudo nano /etc/mosquitto/mosquitto.conf
Most beginner projects can use the default configuration without modification.
Restart Mosquitto After Configuration Changes
Whenever configuration changes are made, restart the broker.
sudo systemctl restart mosquitto
Verify status:
sudo systemctl status mosquitto
Common Installation Issues
Service Not Starting
Check Mosquitto logs.
journalctl -u mosquitto
Port Already in Use
Verify if another application is using port 1883.
sudo lsof -i :1883
Firewall Blocking Connections
Allow MQTT traffic through the firewall.
sudo ufw allow 1883
Reload firewall rules.
sudo ufw reload
Installing Mosquitto on Raspberry Pi
If you’re using Raspberry Pi OS, the installation process is identical to Ubuntu.
Run:
sudo apt update sudo apt upgrade -y sudo apt install mosquitto mosquitto-clients -y
Then enable and start the service:
sudo systemctl enable mosquitto sudo systemctl start mosquitto
Your Raspberry Pi is now ready to run Mosquitto.
For a complete Raspberry Pi MQTT server setup, including static IP configuration, ESP32 integration, Node-RED connectivity, and broker optimization, continue with:
Raspberry Pi MQTT Broker Setup Using Mosquitto
Conclusion
Mosquitto is one of the easiest MQTT brokers to install and an excellent choice for beginners learning MQTT. In just a few minutes, you can set up a lightweight broker capable of handling communication between IoT devices, dashboards, and automation systems.
With Mosquitto running successfully, you’re now ready to connect ESP32 devices, build real-time dashboards with Node-RED, and create complete IoT solutions.
Frequently Asked Questions
What is Mosquitto MQTT Broker?
Mosquitto is a lightweight open-source MQTT broker that enables communication between MQTT publishers and subscribers.
Is Mosquitto free?
Yes. Mosquitto is completely free and open source under the Eclipse Foundation.
Which port does Mosquitto use?
Mosquitto uses port 1883 for unencrypted MQTT communication and port 8883 for MQTT over TLS.
Can Mosquitto run on Raspberry Pi?
Yes. Raspberry Pi is one of the most popular and cost-effective platforms for hosting a Mosquitto MQTT broker.
How do I check if Mosquitto is running?
Use:
sudo systemctl status mosquitto
Can ESP32 connect directly to Mosquitto?
Yes. ESP32 devices can connect directly to a Mosquitto MQTT broker using libraries such as PubSubClient. Once connected, they can publish sensor data and subscribe to control commands.
What is the difference between Mosquitto and MQTT?
MQTT is the communication protocol, while Mosquitto is software that implements an MQTT broker.
