A Closer Look at Modern Industrial Communications Protocols

Industrial environments increasingly rely on data interoperability and efficient communication to improve operations and more. As such, modern industrial communications protocols, such as MQTT (Message Queuing Telemetry Transport) and OPC UA (Open Platform Communications Unified Architecture), are playing a key role in balancing security, efficiency, and flexibility in digital transformation strategies.

Several recent trends are driving the adoption of these protocols. To start, organizations are recognizing the untapped potential of industrial data to enhance efficiency, reduce costs, and increase safety. Going hand-in-hand with such realizations is the rise in the use of advanced analytics and AI. The growing use of these technologies has significantly increased the demand for data collection.

Consequently, companies are investing in technologies to streamline data flow between systems while ensuring usability for both humans and machines. There is also increased attention paid to efficient data transmission and meaningful representation of that data, both of which are essential for driving insights and organizational transformation.

What Differentiates One from the Other?

There are several fundamental distinctions between the two protocols.

OPC UA is a more comprehensive protocol. It is both a modeling language and a wire protocol, meaning it defines how data is structured and how it moves across networks. It makes use of a client-server communication infrastructure in that it supports a peer-to-peer model, where clients (such as SCADA systems) establish direct relationships with servers (data providers).

Additionally, OPC UA is structured and deterministic. It ensures highly structured communication, making it suitable for control operations requiring predictability and reliability.

In contrast, MQTT is considered lightweight and flexible. It only defines data transport, meaning the actual content can be anything (e.g., structured industrial data or even a cat video). It uses a publish-subscribe model that involves an intermediary broker, allowing data producers (publishers) to send information without a direct client connection.

In many cases, it is better for remote and cloud data transfers because it is ideal for sending data outside secure networks and allows outbound-only communication.

MQTT and UPC UA: Details and Use Cases

It is important to keep in mind that there are many communication protocols that are used in industrial settings. However, MQTT and OPC UA are probably the two most commonly used ones in such environments. That said, it is important to understand what each protocol does, when to use one versus the other, and how the two can work together.

MQTT

MQTT is a lightweight, publish-subscribe messaging protocol designed for low-bandwidth, high-latency, and remote communication networks. It is widely used in industrial automation, IoT (Internet of Things), and cloud-based applications where efficient, reliable, and scalable data exchange is required. Some of its most common use cases include:

Industrial Automation

• MQTT enables real-time data collection from sensors, PLCs, and industrial equipment, allowing companies to predict failures and optimize performance.
• MQTT is used in Supervisory Control and Data Acquisition (SCADA) and Industrial IoT (IIoT) systems for secure, event-driven communication.

Smart Manufacturing and Industry 4.0

• MQTT brokers act as centralized data hubs, allowing different factory systems (MES, SCADA, PLCs) to exchange information seamlessly.
• MQTT supports high-frequency data exchange between machines and cloud applications for process optimization.

OPC UA

OPC UA is a cross-platform, service-oriented, industrial communication protocol designed to provide secure, reliable, and scalable data exchange in automation, manufacturing, and industrial IoT (IIoT) environments. It is widely used in factory automation, process control, and industrial data integration to enable seamless interoperability between different devices, applications, and enterprise systems. Some common use cases include:

Industrial Automation and Factory Control

• OPC UA connects Supervisory Control and Data Acquisition (SCADA) systems, Human-Machine Interfaces (HMI), and Manufacturing Execution Systems (MES).
• OPC UA enables real-time data flow between Programmable Logic Controllers (PLC) and other industrial devices.
• OPC UA facilitates Industry 4.0 by allowing machines from different vendors to communicate seamlessly.

Process Control and Real-time Data Monitoring

• OPC UA is used for real-time monitoring of pressure, temperature, and system performance.
• OPC UA enables automated responses to critical system alerts.

A Final Word

While MQTT and OPC UA are suitable for different use cases, they are often used together. Specifically, OPC UA can operate over MQTT, merging structured OPC UA data models with MQTT’s publish-subscribe transport model. Such a hybrid approach enhances interoperability between cloud systems and industrial networks.