MQTT in the Real World

Migrating Legacy Protocols to MQTT

- By Ignacio Siccardi

MQTT is an OASIS standard messaging protocol for the Internet of Things. This lightweight protocol can simplify and improve messages between IoT components that started out using different languages.

Many industrial systems still rely on Modbus, OPC-DA, Profibus, and other legacy fieldbus protocols. While these protocols have served industry well, they present limitations in flexibility, scalability, and cloud integration.

MQTT serves as a bridging solution, enabling seamless migration from legacy systems without requiring complete infrastructure overhauls. Gateways or protocol converters are deployed at the edge to translate legacy data formats into MQTT messages, which are then published to centralized brokers or cloud platforms.

A manufacturing plant uses SCADA with Modbus TCP, integrated with MQTT as a wrapper layer. By employing an edge gateway with Modbus-to-MQTT translation, they maintained existing PLCs while transmitting real-time data to a cloud analytics platform, as shown in Figure 1. This enabled the operations team to monitor key parameters remotely while gradually phasing out the legacy system.

The publish-subscribe nature of MQTT enables decoupling between devices and applications, paving the way for sustainable modernization. This transition approach reduces downtime and risks while allowing gradual integration of AI, ML, and advanced analytics.

REAL-TIME DIAGNOSTICS

Traditional diagnostic methods in industrial settings often depend on periodic polling or manual inspection. These approaches are inefficient, particularly when uptime is critical. MQTT provides a lightweight, event-driven alternative that enables continuous data flow for real-time diagnostics.