Communication via MQTT broker

PLCnext devices running firmware 2024.0 LTS or newer can communicate not just to Proficloud but to any MQTT broker, e.g. those provided by Amazon Warehouse Services (AWS) or Microsoft Azure. This implementation of an MQTT client directly within the firmware is one of many possibilities, along with different apps from the PLCnext Store. Weigh the features and benefits of the available clients and use the one that suits your needs best.

MQTT itself is a lightweight messaging protocol for machine-to-machine communication, based on TCP for the data transport. For a secure connection, Transport Layer Security (TLS) is supported. Several tools and open source libraries for use with a wide array of programming languages and integrated development environment (IDE) software are available. For the detailed specification, basic concepts and tutorials, and a showcase of typical use cases refer to MQTT.org. 

The MQTT protocol is especially useful for data transfer via cloud servers and plays an important role for the Industrial Internet of Things (IIoT). MQTT communication on PLCnext devices uses the out ports that are marked for Proficloud in the PLCnext Engineer dashboard. 

As of now, PLCnext devices can only send (publish) OUT port data to an MQTT broker. The interface for MQTT communication will be extended in further development steps to support more features; such as:

• configuring the Quality of Service
• subscribing to other variables, e.g. IN ports of programs
• running multiple instances of an MQTT client
• subscribing to the same values from different MQTT clients in parallel.

As of now, in case you want to communicate with more than one MQTT broker at a time, you can use the MQTT Client function block provided with the free-of-charge IIoT_Library in the PLCnext Store.