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Read problem

05 Feb 2020 19:20 - 05 Feb 2020 19:20 #8203 by support
Replied by support on topic Read problem
QuickOPC reads NamespaceArray and ServerArray (their Value attributes) as part of opening the session.
NamespaceArray appears usable, but ServerArray returns BadNodeInvalid.
ServerArray is, however, mandatory, and the server is thus not compliant with the OPC UA specification.

You will not be able to connect to this server with QuickOPC until the server is fixed.

Best regards.
Last edit: 05 Feb 2020 19:20 by support. Reason: small typo

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05 Feb 2020 18:07 - 05 Feb 2020 18:10 #8202 by Boris
Read problem was created by Boris

There is a server in public access, here are its parameters:
EndpointUrl: opc.tcp://
UserName: This email address is being protected from spambots. You need JavaScript enabled to view it.
Password: demo123
Security: None, None

This server has a problem with tags. Some attributes cannot be read (see the example in the attachment). But some attributes are readable.
Unfortunately, my program users want to work with this server and read those attributes that can be read. But an error occurs every time I try to read tags through the "ReadValue" function. Therefore, I decided to read only one attribute: "UAAttributeId_DataType" from the tag "NamespaceArray". With the help of UAExpert, I see that this attribute (DataType) is available and can be read. I took the code from the example "..\OPC Labs QuickOPC 2019.2\Examples-COM\OP\UADocExamples\_EasyUAClient\". Changed it like this:
class procedure ReadMultipleValues.DataType;
  Client: OpcLabs_EasyOpcUA_TLB._EasyUAClient;
  ReadArguments1, ReadArguments2, ReadArguments3: _UAReadArguments;
  Arguments, Results: OleVariant;
  I: Cardinal;
  Result: _ValueResult;
  aSession: _UASmartSessionParameters;
  Client := CoEasyUAClient.Create;
  Client.Isolated := TRUE;
  aSession := Client.IsolatedParameters.SessionParameters;
  aSession.UserIdentity.UserNameTokenInfo.UserName := '';
  aSession.UserIdentity.UserNameTokenInfo.Password := 'demo123';
  ReadArguments1 := CoUAReadArguments.Create;
  ReadArguments1.EndpointDescriptor.UrlString := 'opc.tcp://';
  ReadArguments1.NodeDescriptor.NodeId.ExpandedText := 'ns=0;i=2255';   // NamespaceArray
  ReadArguments1.AttributeId := UAAttributeId_DataType;   // DataType attribute
  Arguments := VarArrayCreate([0, 0], varVariant);
  Arguments[0] := ReadArguments1;
  TVarData(Results).VType := varArray or varVariant;
  TVarData(Results).VArray := PVarArray(Client.ReadMultipleValues(Arguments));
  for I := VarArrayLowBound(Results, 1) to VarArrayHighBound(Results, 1) do
      Result := IInterface(Results[I]) as _ValueResult;
      if Result.Succeeded then
          WriteLn('Value: ', Result.Value);
          WriteLn('Value.ExpandedText: ', Result.Value.ExpandedText);
          WriteLn('Value.NamespaceUriString: ', Result.Value.NamespaceUriString);
          WriteLn('Value.NamespaceIndex: ', Result.Value.NamespaceIndex);
          WriteLn('Value.NumericIdentifier: ', Result.Value.NumericIdentifier);
        WriteLn('results(', I, ') *** Failure: ', Result.ErrorMessageBrief);
But again I get the error: "results(0) *** Failure: OPC-UA service result - (no description available) = BadNodeIdUnknown". The same thing when trying to read other attributes.
Is there any way to read those attributes that are readable? Maybe I'm doing something wrong?
Last edit: 05 Feb 2020 18:10 by Boris. Reason: removed duplicate text

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