In shortOPC UA (OPC Unified Architecture) is an industrial communication standard (IEC 62541) for platform-independent, secure and object-based data exchange between machines, PLCs and higher-level systems.
The core idea of OPC UA is to expose data not as a bare number but as a defined object with meaning, unit, quality and timestamp. A server publishes nodes in an address space. A client can browse, read, write, subscribe to changes and call methods on those nodes.
Security is part of the design: application certificates, signing and encryption modes and user authentication are supported. For a connection to be genuinely secure, certificate trust lists must be managed; the OPC UA certificate checklist covers this.
OPC UA is mostly used client/server; a publish/subscribe (PubSub) model is also defined. Industry-specific information models are defined by companion specifications.
In OPC Router projects
In OPC Router, the OPC UA Client reads machine and PLC data and sets up write flows with suitable permissions; the OPC UA Server can expose processed data to OPC UA clients. We confirm endpoint, security mode and certificate trust together in the project.
Frequently asked questions
What is the difference between OPC UA and OPC DA?
OPC DA is the classic version based on Windows COM/DCOM. OPC UA is platform-independent, builds security into its design and supports an information model.
Should I use OPC UA or MQTT?
They solve different problems and are often used together. See OPC UA or MQTT? for details.