OPC UA is a central element of the Industry 4.0 story providing seamless communication between IT and industrial production systems. basysKom has initiated Qt OPC UA in 2015 with the goal of providing an out of the box Qt API for OPC UA. In 2017 basysKom, together with The Qt Company, has finished up a Technology Preview of that API. It will be available with the upcoming Qt 5.11 release end of May.

The focus of Qt OPC UA is on HMI/application development and ease of use for client-side development. The Tech Preview implements a subset of the OPC UA standard. It allows to connect to servers, read and write attributes, call methods on the server, monitor values for data changes and browse nodes. All this functionality is provided by asynchronous APIs which integrate nicely into Qt applications.

Qt OPC UA is primarily an API and not a whole OPC UA stack. A plugin interface allows to integrate existing OPC UA stacks as API backends. Currently, plugins for the following stacks are available:

• FreeOpcUa
• open62541
• Unified Automation C++ SDK 1.5

Qt OPC UA will be available directly from the Qt installer for those holding a Qt for Automation license. The source code itself is triple licensed (GPL, LGPL and commercial) with the exception of the Unified Automation backend which is only available under a commercial license. Users of one of the Open Source licenses will need to compile Qt OPC UA themselves. See here for a list of build recipes.

The backends for FreeOpcUa and open62541 are available under an Open Source license. When going for an Open Source solution, we recommend the open62541 plugin as it is the more complete implementation with an active community and a good momentum. It also has less dependencies, making usage on platforms such as Android or iOS much easier.

On the platform side, the technology preview will by available for

• Windows with Visual Studio 2015 & 2017 as well as MinGW
• Linux (Desktop and Embedded)
• Android and iOS

Please note that not every backend is available on every platform.

On top of what is part of the Tech Preview, there are already a number of additions planned. Among them support for transport security, the discovery service, event support and filters.

We are looking forward to feedback and questions on this new module.