Installing the Mosquitto MQTT Server on the Raspberry Pi?

The MQTT protocol is a lightweight messaging protocol that works on top of the TCP/IP protocol. It is designed for connections with remote locations where a small code footprint is required or network bandwidth is limited. Raspberry Pi devices are low powered single board computers that are perfect for using as MQTT servers.

Installing the Mosquitto MQTT Server on the Raspberry Pi?

Reasons to Use Mosquitto MQTT on Raspberry Pi

Here are some of the main reasons you may want to install Mosquitto MQTT on a Raspberry Pi:

  • MQTT is lightweight and perfect for IoT devices like Raspberry Pi with limited resources.
  • Mosquitto is an open source MQTT server that is easy to install and configure.
  • You can use a Raspberry Pi MQTT server to connect remote sensors, devices, etc and manage them from a central server.
  • Setting up remote locations is simplified by using MQTT’s publish/subscribe messaging pattern.
  • MQTT brokers like Mosquitto allow messages to be queued when devices are offline, then forwarded when they reconnect.
  • Mosquitto uses very little processing power and memory compared to alternatives.

Step 1: Install Mosquitto on the Raspberry Pi

Installing Mosquitto on Raspberry Pi only takes a few quick terminal commands. Log into your Pi and type:

sudo apt update

sudo apt install mosquitto

This will get the latest package information and install the Mosquitto package and dependencies.

Step 2: Configure the MQTT Server

The default Mosquitto config file location is /etc/mosquitto/mosquitto.conf. Open this file in nano or your preferred text editor:

sudo nano /etc/mosquitto/mosquitto.conf

  1. Disable anonymous user access – By default anonymous clients can connect, disable this:
  2. allow_anonymous false
  3. Set the listener port – if needed, the default listener port is 1883
  4. port 1888
  5. Enable logging – Good for debugging connection issues

persistence true

persistence_location /var/lib/mosquitto/

  1. log_dest file /var/log/mosquitto/mosquitto.log
  2. This will log activity to the mosquitto.log file.
  3. Save changes – Ctrl-X to exit, confirm save by pressing Y, then Enter

Step 3. Secure the MQTT Mosquitto Server

For security its best practice to require user authentication for connecting to MQTT. There a few ways to implement this, here are some options:

A. Password File Authentication

  1. Create a passwords file:
  2. sudo touch /etc/mosquitto/pwfile
  3. Use mosquitto_passwd utility to add users:
  4. sudo mosquitto_passwd -c /etc/mosquitto/pwfile user1
  5. Enter and confirm the user password.
  6. In mosquitto.conf, set the file:
  7. password_file /etc/mosquitto/pwfile
  8. Restart mosquitto after config changes:
  9. sudo systemctl restart mosquitto

Clients must now provide authorized username and password to connect.

B. TLS Encryption

For enhanced security, TLS encryption can be enabled:

  1. Obtain or generate an SSL certificate:
  2. openssl req -new -x509 -days 365 -nodes -out mosquitto.crt -keyout mosquitto.key
  3. Add the following to mosquitto.conf:

listener 1883

listener 8883

cafile /etc/mosquitto/mosquitto.crt

certfile /etc/mosquitto/mosquitto.crt

keyfile /etc/mosquitto/mosquitto.key

  1. tls_version tlsv1.2
  2. Restart mosquitto to apply changes. Clients can now connect securely to port 8883.

Step 4: Test MQTT Connectivity

Lets do a quick test to validate the MQTT server is functioning:

  1. Open a new terminal session and connect using the mosquitto_sub client:
  2. mosquitto_sub -h localhost -t testtopic
  3. Open another terminal and send a test message:
  4. mosquitto_pub -h localhost -t testtopic -m “Hello MQTT”
  5. Verify that the message appears in the subscriber terminal. Congrats you now have a working MQTT server!

Troubleshooting Mosquitto

Here are solutions for common issues:

  • Connection refused – Verify config file settings like password_file match credentials
  • Authentication failures – Check username and password match pwfile entries
  • Subscribers not receiving messages – Clients must match the exact topic string to receive messages
  • Loss of messages – Set persistence true and a persistence_location to enable message queueing
  • TLS / SSL issues – Confirm keys and certs files match config entries

Optimizing the Raspberry Pi for MQTT Performance

Even on low power devices like Raspberry Pi, a few optimizations can enable an MQTT server to support many remote clients:

  • Set a static IP address to maintain access after reboots
  • Use a memory split to allocate more RAM to Linux system processes
  • Enable CGroups to limit and prioritize MQTT resource usage
  • Overclock the CPU and GPU for a little extra performance
  • Operate the server headless without desktop for lower overhead
  • Connect sensors and devices to GPIO pins to avoid USB bottlenecks
  • For higher loads, consider distributing brokers across multiple Pis
  • Or use more capable hardware like Raspberry Pi 4

Key Takeaways and Conclusion

A few key things to note in summary about installing Mosquitto MQTT on a Raspberry Pi:

  • MQTT is lightweight, making it perfect for small devices
  • Configuration controls security, performance, persistence
  • Simple test tools like mosquitto_pub and mosquitto_sub help verify connectivity
  • Password files or TLS encryption should be used to secure MQTT
  • Tuning options like overclocking provide optimization for higher loads
  • Multiple broker distribution is possible for large number of clients

Setting up a Mosquitto server on Raspberry Pi only takes a few minutes. The lightweight MQTT messaging protocol was designed exactly for low resource IoT devices. With clients able to publish and subscribe to remote feeds, it opens up many possibilities for sensors, automation, and remote control projects across small distances or around the world.

Frequently Asked Questions

  1. What is MQTT?
    MQTT stands for Message Queuing Telemetry Transport. It is an ISO standard messaging protocol designed for lightweight machine to machine communications with remote locations and IoT devices.
     
  2. How does MQTT work?
    MQTT uses a publish/subscribe pattern. Clients subscribe to topics/feeds to receive messages published from other clients. Messages don’t go peer to peer but through a central MQTT message broker.
     
  3. Why use MQTT on Raspberry Pi?
    MQTT places little demand on device hardware with a small code footprint, making it an ideal protocol for resource constrained devices like the Raspberry Pi for IoT applications.
     
  4. What does Mosquitto do?
    Mosquitto is an open source MQTT message broker (server) that handles network connections, topic subscription, and delivery of messages between MQTT clients.
     
  5. Is Mosquitto secure?
    By default Mosquitto allows anonymous access which would not be secure. But password and TLS encryption options can be configured to authorize clients and encrypt data.
     
  6. Can you distribute MQTT brokers?
    Yes, it is possible to design an MQTT system with multiple distributed message brokers handling a subset of clients, queues, or topic feeds. This may help scale an MQTT implementation.
     
  7. Does MQTT work offline?
    Yes, the persistence feature of MQTT allows queued messages to be saved until remote devices regain connection. When back online messages are then forwarded. This makes MQTT resilient for intermittent connections.
     
  8. Can I run MQTT over WiFi?
    Yes, as MQTT runs over TCP it can operate over TCP/IP networks like WiFi. Performance may vary for latency sensitive use cases verses wired networks.
     
  9. Can multiple clients connect to a topic?
    Yes, in MQTT a topic can have an unlimited number of publishing clients and subscribing clients. This one to many message distribution is a core concept behind MQTT.
     
  10. Is MQTT faster than HTTP?
    Yes in most cases as MQTT uses fewer protocol handshakes and less overhead than HTTP requests between client/server transfers.
     
  11. Does MQTT require a gateway?
    A higher level MQTT gateway provides features like protocol/format adaptation, client libraries, administrative functions, etc. But simple implementations can also directly connect MQTT clients to an MQTT broker.
     
  12. Is MQTT the same as Websockets?
    No, Websockets and MQTT address somewhat different concerns. Websockets enables persistent bidirectional communication on a single TCP socket. MQTT uses multiple sockets to enable centralized one to many messaging across a network.
     
  13. What hardware does MQTT work on?
    MQTT can be implemented on most devices that support TCP/IP networking. From microcontrollers, RPi, servers, phones, to laptops. If it can connect to a network, it can use MQTT.
     
  14. Can MQTT work on the Raspberry Pi Zero?
    Yes, the stripped down RPi Zero and Zero W with only 1 core can still run Mosquitto MQTT perfectly fine for light workloads thanks to the efficiency of MQTT.
     
  15. Is MQTT reliable for critical systems?
    MQTT scales well and has reliability mechanisms built-in, but mission critical industrial systems may have additional needs like guaranteed delivery requiring additional protocols.
     
  16. Why choose Mosquitto over HiveMQ or RabbitMQ?
    Mosquitto is lightweight, open source, and specifically built for MQTT. HiveMQ and RabbitMQ support MQTT but also other protocols with extra features, making them more complex to configure.
     
  17. Can I distribute load across multiple MQTT brokers?
    Yes, it is possible to spread load using multiple parallel MQTT brokers – clients connect to one directly while still allowing subscription to topics published to other brokers in the cluster.
     
  18. How many MQTT clients can a RPi handle?
    Performance depends on usage, but Raspberry Pi 2-4 devices should handle at least 50-100 active MQTT clients publishing moderate message volumes. Fine tuning OS parameters can further improve this capacity.
     
  19. What are common MQTT implementations?
    Some examples are – home automation tasks like controlling lights, temp sensors, smart devices, etc. Fleet tracking of vehicles. Connecting remote sensors in widespread locations like farms, windmills or pipelines. Supply chain monitoring of inventories, logistics in transit.

  20. Can I use MQTT over the internet or just locally?
    MQTT can be used over LANs or WANs like the public internet by connecting the broker to a public IP address and handling port forwarding and firewall rules.

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