Alternative OPC-UA back-ends for quasar

• The UA C++ SDK, version 1.3.x, 1.4.x, 1.5.x.
  Note that you can use the evaluation version of the UA C++ SDK in case you don't have the regular license.
  Note this back-end works directly in quasar and we don't support any further instructions.
  
• The open62541 used through open62541-compat
  Read below.

Using open62541 (open-source OPC-UA stack)

The open62541 is a C-based OPC-UA stack and on its own it can't be used as a back-end for Quasar.

Therefore, the Quasar team has created a compatibility layer which lets use open62541 in quasar projects. The compatibility layer is quickly available to quasar developers as one of supported "optional modules".

Note that the procedure requires to posses the build config file for open62541 - at the moment, you can obtain it from Piotr.Nikiel@cern.ch
The quasar team is working on a more sustainable way to distribute it.

In order to configure your quasar project to use the open62541, follow the steps (it is assumed you already have a quasar project):

1. Enable open62541-compat in your project
   ./quasar.py enable_module open62541-compat
2. Set build configuration for open62541
   ./quasar.py set_build_config <your open62541-config file>
   
3. Download all required quasar modules
   ./quasar.py prepare_build
   
4. Prepare open62541-compat (it will download and compile open62541 itself)
   cd open62541-compat/
   python prepare.py
   cd ..
   
5. Run the build:
   ./quasar.py build
   

Configuring open62541: endpoint urls, etc.

Quasar makes full use of UA SDK ServerConfig.xml to configure things like:

• endpoint(s) to open (including port numbers, etc)
• Application/Product URI(s) - relevant when discovery service is used
• Discovery servers to register on
• Behavioural settings, like the max polling frequencies, etc.

Unfortunately, support for ServerConfig.xml is not yet there when the open62541 is used as a backend. The ticket to follow is:

https://its.cern.ch/jira/browse/OPCUA-686

Changing the defaults must generally be hardcoded, e.g.  look at the constructor in Server/src/opcserver_open62541.cpp.
m_server_config is the object storing the configuration for the server when open62541 is used.

OPC-UA Back-end dependent features: a comparison table