MQTT Protocol: Functionality, Applications and Benefits in the IoT

In the Internet of Things (IoT), communication protocols form the foundation for data exchange between devices and applications. The MQTT protocol (Message Queuing Telemetry Transport) is a lightweight publish-subscribe protocol developed specifically for low-resource devices and low-bandwidth networks. It ensures reliable MQTT communication, even in high-latency or unstable connection environments. This article explains how MQTT works, which devices use it and what advantages it offers companies in the IoT.

MQTT was originally developed in 1999 by Andy Stanford-Clark (IBM) and Arlen Nipper (Arcom) to enable the monitoring and remote control of oil and gas pipelines via satellite connections. Today, it is an integral part of many IoT applications – from connected household devices to complex industrial control systems. 

Its strength lies in its lean architecture: MQTT requires only minimal network resources and is therefore ideally suited for low-power devices such as battery-powered sensors or actuators.

The MQTT protocol is based on a publish-subscribe model that makes data exchange between different MQTT devices particularly efficient. Three core components assume fixed roles:

• Publisher: Sends messages on a specific topic to the broker
• Subscriber: Receives messages on subscribed topics
• Broker: Mediates between publishers and subscribers and ensures reliable message delivery 

Unlike classic client-server structures, publishers and subscribers do not communicate directly with each other. Instead, the broker handles the entire MQTT communication, enabling low latency and a stable connection.

MQTT can be seamlessly integrated into cloud platforms such as AWS IoT Core, Azure IoT Hub or private enterprise clouds. For smooth data transmission, however, devices require stable and energy-efficient connectivity. With suitable IoT solutions  and networks such as NB-IoT or LTE-M , companies can operate MQTT applications securely worldwide.

The MQTT protocol is used by a wide variety of devices that are part of IoT ecosystems. These are typically applications where low bandwidth, low power consumption and reliable communication are critical. 

The MQTT protocol is highly versatile and suitable for numerous IoT scenarios. Its lightweight design makes it ideal for almost any type of IoT communication – from simple sensor data to the control of complex systems.

• Real-time transmission of sensor data: Temperature, humidity or motion readings are sent directly to central systems or dashboards.
• Remote control of devices: Machines, lighting or heating systems can be controlled via MQTT commands.
• Smart home automation: Washing machines, lights or charging stations respond automatically to predefined events or favourable electricity tariffs.
• Industry 4.0: Production systems and manufacturing lines communicate via MQTT to optimise utilisation and maintenance intervals.
• Fleet and logistics management: Vehicles send location and status information to the control centre in real time.

A central component of many MQTT installations is Eclipse Mosquitto, an open-source MQTT broker under the Eclipse Foundation. It implements the publish-subscribe model seamlessly. Running Eclipse Mosquitto on a server requires only a simple system such as a Raspberry Pi or a small cloud server. 

Implementation typically involves just a few steps:

1. Installing the Mosquitto broker on the desired system (Linux, Windows, macOS, embedded devices)
2. Configuring ports, topics and security options
3. Integrating publisher and subscriber clients
4. Testing and monitoring MQTT communication

The MQTT protocol has established itself as one of the most important standards for efficient, reliable and scalable data transmission in the Internet of Things. Especially in environments with many devices, unstable networks or limited resources, it offers clear technical and economic advantages.

• Resource-efficient – ideal for battery-powered sensors and other MQTT devices with limited computing power.
• High reliability – with selectable QoS levels, messages are delivered reliably even over unstable connections.
• Scalability – from small sensor networks to global IoT platforms  with millions of clients.
• Optimised bandwidth usage – minimal overhead data ensures efficient communication.
• Interoperability – MQTT is platform-independent and compatible with numerous programming languages, operating systems and cloud platforms.
• Flexibility – easy integration into existing systems, including cloud services such as AWS IoT Core or Azure IoT Hub.

Quality of Service defines how reliably messages are delivered in the MQTT protocol. 

QoS 0 – “At most once”: Message is sent at most once, no confirmation. 
QoS 1 – “At least once”: Message is sent at least once, receiver acknowledges receipt. 
QoS 2 – “Exactly once”: Message is delivered exactly once, highest level of reliability.

When implementing the MQTT protocol, IoT security  is a central issue. As MQTT is designed for resource-efficient communication, security must be deliberately addressed during the implementation phase. Only then can data integrity, availability and confidentiality be ensured in the long term. 

• Encryption with TLS/SSL: Protects messages from unauthorised access during transmission.
• Strong authentication: Combination of username/password or certificate-based authentication.
• Topic-based rights management and authorisation: Only authorised clients may publish or receive specific data.
• Broker-level access control: Use of firewalls and IP whitelists.
• Monitoring and logging: Continuous monitoring of broker performance and login attempts.

The MQTT protocol has established itself as one of the key standards in IoT communication. Its lean architecture, high reliability and simple scalability make it ideal for companies that want to seamlessly connect devices, applications and platforms. Whether for MQTT devices in the smart home, in industry or in large-scale IoT infrastructures: the protocol ensures smooth data transmission even under challenging network conditions. 

Combined with energy-efficient IoT connectivity such as NB-IoT or LTE-M and suitable IoT solutions, it enables a future-proof infrastructure for almost every industry. Companies that strategically deploy MQTT benefit from lower operating costs, higher efficiency and the ability to realise new digital business models.