OPC UA (Open Platform Communications Unified Architecture) is a platform-independent standard through which various types of systems and devices can communicate by sending request and response messages between clients and servers or similarly to MQTT via a subscription-publishing model.

The characteristics of OPC UA are:

• Often used as a standard in manufacturing area
• Robust server/client architecture
• Secure communication and access
• Platform & hardware independent

OPC UA servers define the services they can provide to clients, an object model that can be dynamically discovered by clients and a data model following the data-types defined in the protocol itself.