MQTT

In this article

» What is MQTT?
» How does  MQTT work?
» Why was MQTT created?
» The benefits of MQTT
» What makes the protocol lightweight?
» Who uses MQTT?
» Why is this protocol ideal for SCADA?
» MQTT and Ignition
» Explore Ignition

What is MQTT?

MQTT (Message Queuing Telemetry Transport) is a lightweight messaging protocol designed for efficient communication between devices in low bandwidth, high-latency, or unreliable network environments, such as those found in IoT (Internet of Things) applications.

The protocol follows a publish/subscribe model, where clients connect to a broker and publish messages to a specific topic or subscribe to receive messages about a topic. The broker is responsible for routing messages to the appropriate clients based on their subscriptions.

One of the key advantages of MQTT is its lightweight nature, making it ideal for use in resource-constrained environments, such as small embedded systems. The protocol also supports Quality of Service (QoS) levels, allowing clients to specify the reliability of message delivery.

It is a popular protocol for IoT applications because it enables devices to communicate with each other over the internet in a simple and efficient manner while minimizing network overhead and power consumption.

How does MQTT work?

It operates based on a publish/subscribe model. In this model, devices communicate with each other through an MQTT broker, which acts as an intermediary that forwards messages to the appropriate devices.

The basic components of the protocol are:

• Clients: these are the devices that want to exchange data. This could be, for example, a sensor measuring data and wanting to forward it to another device.
• Broker: this is the central point in the MQTT network. All clients communicate with the broker, which receives messages and forwards them to the appropriate clients.
• Topics: a topic is a label attached to a message. This allows the broker to forward the message to the correct clients that have subscribed to that specific topic.

The process of exchanging data via MQTT unfolds as follows:

1. A client publishes a message to the broker, including the topic to which the message is directed.
2. The broker receives the message and forwards it to all clients subscribed to that specific topic.
3. Clients that receive the message can process the information or respond with their own message.
4. The process can repeat with other clients also publishing messages and subscribing to specific topics.

The protocol is bidirectional and maintains stateful session awareness. If an edge-of-network device loses connection, it notifies all subscribed users using the “Last Will and Testament” feature of the MQTT server, enabling any authorized user in the system to publish a new value to the edge-of-network devices, thus maintaining bidirectional connectivity.

Why was MQTT created?

It is designed to enable efficient communication between devices with limited resources in environments characterized by low bandwidth, high latency, and unreliable networks. The protocol was originally developed by Dr. Andy Stanford-Clark and Arlen Nipper in 1999.

The design was inspired by the need for a reliable, flexible, and efficient means of communication between field devices such as sensors and actuators. The goal was to create a protocol that would facilitate the collection and distribution of large amounts of data from various locations while minimizing network and device overhead.

In the years since the development of MQTT, the protocol has evolved into a key standard for IoT applications. It has become one of the primary protocols for collecting and transmitting data between devices in the IoT sector and is supported by various IoT platforms and cloud services.

The benefits of MQTT

MQTT offers several advantages compared to other communication protocols:

• Lightweight and efficient: It is designed to operate with devices that have limited resources, such as sensors and actuators often powered by batteries. The protocol uses minimal bandwidth and resources to transmit data, minimizing the load on the network and devices.
• Flexible and scalable: It is highly flexible and can be used for a wide range of IoT applications, from collecting sensor data to controlling actuators. Additionally, MQTT is easily scalable to meet the needs of large-scale IoT applications.
• Reliable and secure communication: It supports various levels of Quality of Service (QoS) to ensure reliable data transfer, even in low-bandwidth or high-latency environments. The protocol also supports SSL/TLS encryption to secure communication.
• Easy integration with other systems: It seamlessly integrates with other systems and platforms, such as cloud services and databases, making it an ideal solution for collecting and integrating data from various sources.
• Works well in case of connectivity issues: It can also operate in offline mode, storing and forwarding messages once connectivity is restored. This makes it an ideal solution for IoT applications where network connections may be unreliable.

What makes the protocol lightweight?

MQTT is lightweight for several reasons:

1. Minimal overhead: It is designed to have minimal overhead and uses minimal network bandwidth. Messages are sent in a binary format, and there is no extra information or metadata sent with the messages.
2. Efficient encoding: It employs efficient encoding techniques to minimize the size of messages, allowing messages to be sent and processed faster.
3. Asynchronous communication: It utilizes asynchronous communication, meaning there is no need to maintain a constant connection between the client and the broker. This reduces overhead and makes communication more efficient.
4. Small codebase: The codebase of MQTT is small and straightforward, making implementation and use of MQTT in embedded systems and other lightweight devices easier.

These factors have made MQTT a popular choice for transmitting messages between lightweight devices and systems with limited resources, such as Internet of Things (IoT) devices and mobile applications.

Who uses MQTT?

It was originally developed for low-bandwidth and high-latency data connections used in the oil and gas industry. However, MQTT is now also used by many other organizations and applications.

Many IoT devices use MQTT to enable communication between devices with limited resources, such as sensors and actuators. This includes everything from smart thermostats and security cameras to smart lighting systems and industrial sensors.

MQTT is used in many industrial automation systems, including SCADA, which collect and analyze data to optimize processes.

Telecommunication networks use MQTT to monitor and manage network infrastructure, such as routers, switches, and other devices.

MQTT is used in the transportation sector to assist in vehicle tracking and collecting information on traffic flows, thereby optimizing traffic flow and reducing delays.

In healthcare, MQTT is used to collect data from medical devices and sensors, such as heart monitors, blood pressure monitors, and glucose meters, to monitor patients’ health and alert caregivers if any issues arise.

Why is this protocol ideal for SCADA?

• Efficiency: It is a lightweight protocol, meaning it uses minimal bandwidth and resources to communicate. This is particularly important in SCADA systems where communication occurs over limited network bandwidth.
• Reliability: It supports three levels of Quality of Service (QoS) – QoS0, QoS1, and QoS2 – allowing the system to manage the reliability of data transfer. This is crucial for SCADA systems where data reliability is critical.
• Scalability: It is designed to scale easily, meaning it can support large numbers of devices and sensors collecting and transmitting data. This is a significant consideration for SCADA systems collecting large amounts of data from various locations.
• Security: It provides built-in security options, such as the ability to use SSL/TLS encryption.

Overall, MQTT provides efficient, reliable, and secure communication for SCADA systems, making it an ideal choice for implementing SCADA applications in various sectors such as energy, oil and gas, manufacturing and automation, and water and wastewater industries.

MQTT and Ignition

Ignition is a widely used software platform for industrial automation and SCADA systems. The platform offers powerful tools for collecting, analyzing, and visualizing data from various industrial devices and sensors. MQTT is a popular communication protocol often used in conjunction with Ignition.

• Easily connect to MQTT brokers to receive and process data from MQTT devices and sensors.
• Publish data to MQTT brokers, allowing other systems and devices access to the collected data.
• Visualize and analyze MQTT data using powerful graphical tools and dashboards.
• Integrate MQTT data with data from other sources, such as databases and PLCs, creating a comprehensive view of industrial processes.
• Generate alarms and reports based on MQTT data, enabling operators to quickly respond to changes in industrial processes.

Did you know…

Co-inventor Arlen Nipper currently serves as the president at Cirrus Link Solutions? This company is a strategic partner of Inductive Automation (the creators of Ignition) and has developed Ignition MQTT modules. These modules provide powerful tools for integrating MQTT communication into Ignition SCADA systems and enable bidirectional communication between Ignition systems and MQTT devices and sensors. Arlen Nipper has thus furthered the adoption of MQTT in industrial automation.