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Browse Nodes: Getting empty references in some OPC Clients for an object of type FunctionalGroupType
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Dipika Khera
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09/04/2020 - 00:33
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Hi Team,

 

I've an OPC UA server (Siemens-S7) having some model defined in it. Which consist of an object of type FunctionalGroupType which contains another object of type BaseObjectType having some variables & properties as children.

Hierarchy:

    Object-A (FunctionalGroupType)

       |

       Object-B (BaseObjectType)

             |

             Variable-1 (Int)

             Variable-2 (String), etc.

When I am trying to browse Object-A, some clients like Softing/Prosys are able to browse it. But, in some client it returns Empty References. I tried creating similar model in another OPC-UA server & it was working for me (For this, I had used OPC-UA SDK to create console OPC-UA server & don't have Siemens-S7 configured at my end. Imported DI 1.2 nodeset.xml as well).

 

I tried reading specifications including DI specs & Googled as well but, didn't get any thing.

 

Could you please give some pointers around what could be the possible reason for this ? 

 

FYI: In the earlier case, there are some custom ReferenceTypes, VariableTypes & ObjectTypes defined in model. But, in later not.

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Randy Armstrong
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09/04/2020 - 09:17
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What are you calling an "empty reference"?

Sounds like a server bug.

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Dipika Khera
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09/06/2020 - 23:31
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Thank you Randy for quick response.

 

Below are the steps when I am trying to browse above mentioned hierarchy of nodes:

  1. BrowseRequest made with parameters (NodeId, BroswseDirection.Both, NodeClass.All, BrowseResultMask.All, IncludeSubtypes=True)
  2. Got result of browsing node
  3. StatusCode is Good for Browse call
  4. Checking if there are any references available in browse results via results.getReferences() method call
  5. Got empty list of references here; reference list size is zero
  6. ContinuationPoint is also null.
  7. No children visible in client for browsed Node.

Please let me know if you need any other information.

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Randy Armstrong
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09/07/2020 - 07:12
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Try adding a ReferenceTypeId. If it works it is bug in the server.

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Dipika Khera
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09/07/2020 - 07:49
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Thank you Randy. Let me try to browse it with ReferenceTypeId.

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Dipika Khera
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09/09/2020 - 04:15
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One more question I've, is there any impact of difference in Siemens CPU ? e.g., one server have CPU 1517-3 & other server have CPU 1511C devices connected ?

Try adding a ReferenceTypeId. If it works it is bug in the server.

Do you mean OPC server may have some issue ?

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Randy Armstrong
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09/09/2020 - 21:44
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I don't know about the Siemens products.

A null referencetypeid is valid according to the spec. if the server returns nothing with a null referencetypeid but something with a non-null referencetypeid then the server is not following the spec.

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Dipika Khera
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09/10/2020 - 05:31
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Ok, Got it. Thank you RandySmile

I'll check on this & will share comments on analyzing this issue. I may need some time to check on this part. I'll keep posting about the results I get during analysis.

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Dipika Khera
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09/16/2020 - 07:01
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This issue is resolved now. 

There are some updates pending at server end & the OPC server was acting a proxy server. After installing updates on proxy server, communication between PLC & OPC server started working.

Thank you Randy for all your support.

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