Alternative OPC-UA back-ends for quasar

Here, the term “OPC-UA back-end” refers to a piece of software, which
provides an API compatible with the Unified Automation C++ SDK (note
not all features of the UA API are actually used in quasar).
Quasar supports multiple OPC-UA back-ends.
As of June 2016, the following backends are supported in 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):

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

Feature		UA SDK 1.3+	o pen62541-compat (TODO: version)
Ca che-variables
	Data Types: Boolean, SByte (~signed char), Byte (~unsigned char), Int16, UInt16, Int32, UInt32, Int64, UInt64, Float, Double, String, ByteString	✓	✓
	Variant Data Type (supporting the data types listed above)	✓	✓
	Null Data Type	✓	✓
	Access rights (r/w/rw control)	✓	x
	No-sampling mode for cache-variables	✓	x
Sou rce-variables			x
	Support for same data types as with cache-variables	✓	x
	Synchronous read/write handling	✓	x
	Asynchronous read/write handling	✓	x
Methods
	Support for same data types as with cache-variables	✓	✓
	Synchronous invocation	✓	✓
	Asynchronous invocation	x	x
Calculated items		(broken)	x
Standardized back-end configuration (Se rverConfig.xml)		✓	x