CODESYS-MQTT
MQTT client library for CODESYS PLC programming environment supporting all QoS levels with high performance.
What is CODESYS-MQTT?
CODESYS-MQTT is an MQTT client library built for the CODESYS PLC development environment, enabling programmable logic controllers to communicate using the MQTT publish-subscribe protocol. It solves the problem of integrating industrial automation systems with modern IoT architectures by providing reliable, QoS-aware messaging directly from PLC code. The library supports all MQTT quality-of-service levels, TLS encryption, and multi-broker connections.
Industrial automation engineers and PLC programmers using CODESYS who need to connect their controllers to MQTT-based IoT systems, SCADA platforms, or cloud services.
Developers choose CODESYS-MQTT for its high-performance architecture that delivers packets within the same PLC cycle, comprehensive MQTT feature support including all QoS levels, and seamless integration with CODESYS through callback-driven function blocks that eliminate manual topic string handling in programs.
Overview
MQTT client library for CODESYS, supporting all QoS
Use Cases
Best For
- Connecting CODESYS-based PLCs to MQTT brokers for IoT data collection
- Implementing industrial IoT (IIoT) communication in automation projects
- Bridging operational technology (OT) systems with IT infrastructure via MQTT
- Building real-time monitoring systems for industrial equipment using MQTT
- Creating CODESYS applications that publish sensor data to cloud platforms
- Developing PLC programs that subscribe to MQTT topics for remote control
Not Ideal For
- Projects not using the CODESYS PLC programming environment, such as those with generic C++ or Python applications
- Applications requiring thread-safe MQTT client operations in multi-threaded or concurrent systems
- Teams prioritizing extensive official documentation and broad community support over raw performance optimization
- Simple IoT prototypes where a lightweight, standalone MQTT client with cross-language support suffices
Pros & Cons
Pros
Delivers received packets within the same PLC cycle and handles 50 QoS 0 packets per cycle in default configuration, ensuring real-time communication for industrial applications.
Uses callbacks for subscription handling, enabling dynamic instance creation and eliminating manual topic string entry in programs, as shown in the MyProperty example.
Supports all QoS levels, TLS encryption without certificates, will topics, retain options, and multi-broker connections, covering essential protocol needs.
Provides dedicated function blocks for transmitting values and states with minimal configuration, reducing setup overhead for common tasks.
Cons
The library explicitly states the client is not thread-safe, limiting its use in multi-threaded CODESYS applications or when integrating with concurrent systems.
The README is brief and relies on external integration guides, which may hinder onboarding and troubleshooting for developers new to MQTT or CODESYS.
All required libraries are hosted on the same GitHub account, creating a potential single point of failure and limiting community-driven enhancements.
Frequently Asked Questions
Related Projects
mqtt2opcuaMQTT to OPCUA protocol converter/gateway
spicierModbus2mqttModbus master which publishes via MQTT
OPC RouterMQTT Gateway (publisher/subscriber) with various plug-ins (OPC UA Bridge, SQL Bridge, REST Bridge, SAP Bridge)
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