Hello World example for OPC UA Client

[atimin]

Is your feature request related to a problem? Please describe.

There is no documentation for the OPC UA Client part of the stack.

Describe the solution you'd like

We need a document in 'Getting started' part, that describes OPC UA conection establishment and data reading with ASNeG OPC UA Client.

[wedvjin]

Hi @flipback , Reckon we could together tackle this?

So far, with helloworld server running if the client is run as:

$ OpcUaClient3 -command FindServer

getting:

DBG [7f15a1521740] init namespaces
client service for command FINDSERVER error: get client access object failed: Session=OpcUaClient

That is using built in client; how would you get started writing the client part of the application?

So far I have found client example in: https://github.com/ASNeG/ASNeG-Demo/blob/master/example/ValueBasedInterface/src/SyncReadFromServer.cpp

Edit: I have connected to the server from terminal by issuing the following command:

$ OpcUaClient3 -Command Connect -EndPointurl opc.tcp://127.0.0.7:8888

[atimin]

Hi @wedvjin , FindServer service is not implemented on the server side by default. We planned to do it in a separeted project - https://github.com/ASNeG/OpcUaDiscoveryServer

But the error message from the client looks strange anyway. I'll try to look into the weekends.

[wedvjin]

Hi @flipback , I would be very grateful if you could point me into the right direction of compiling the client application utilizing the stack. So far I've got to based on the SyncReadFromServer.cpp trying to compile with:

$ g++ -Wall -I. -lboost_system Client.cpp -o test

But I get enormous errors so that is probably not the intended way.

[wedvjin]

To update on my findings: I have managed to compile the client app using cmake and appropriate makefiles. Right now with helloworld server running and when trying to connect to it with a client getting assertion error in one of the core's methods:

DBG [7f1caf12c3c0] service set manager starts io thread: IOThreadName=<VBIClient>
DBG [7f1ca96d1700] start thread: ThreadId=<7f1ca96d1700>
INF [7f1ca96d1700] resolver complete
INF [7f1ca96d1700] connect secure channel to server: Address=<127.0.0.1>, Port=<8888>
INF [7f1ca96d1700] secure channel to server connected: Address=<127.0.0.1>, Port=<8888>
SimpleClient: /home/user/OpcUaStack/src/OpcUaStackCore/SecureChannel/SecureChannelBase.cpp:520: void OpcUaStackCore::SecureChannelBase::asyncWriteOpenSecureChannelRequest(OpcUaStackCore::SecureChannel*, OpcUaStackCore::OpenSecureChannelRequest&): Assertion `applicationCertificate().get() != nullptr' failed.
Aborted (core dumped)

I am going to continue my research, but in the meantime if you get any clues please let me know. Many thanks

[huebl]

Hi @wedvjin ,

The client needs a certificate and a crypto manager. You can find some examples in the test section of the project.

VBI Interface https://github.com/ASNeG/OpcUaStack/blob/master/tst/OpcUaStackClient/ValueBasedInterface/VBIAsyncReal_Attribute_t.cpp

    connectContext.applicationCertificate_ = applicationCertificate;
    connectContext.cryptoManager_ = cryptoManager;

Session Service Interface https://github.com/ASNeG/OpcUaStack/blob/master/tst/OpcUaStackClient/ServiceSet/ServiceSetManagerAsyncReal_Attribute_t.cpp

sessionServiceConfig.secureChannelClient_->applicationCertificate(applicationCertificate);
sessionServiceConfig.secureChannelClient_->cryptoManager(cryptoManager);

There are also examples of synchronous use of the interface.