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‘Access denied’ + The client method called was 'BrowseProperties'.

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03 Aug 2021 04:44 #10088 by support
Hello.

The screenshot of the "other error" is missing. However, OPC analyzer isn't suitable to troubleshoot issues like this, because putting it in middle completely changes precisely the part that needed to be diagnosed.

I am not saying it is a "DCOM issue"; I wanted to say it might be possible to resolve by tweaking DCOM, even when other clients do not need it.

There really isn't anything else I can offer.
Note: I am on vacation this week, replies take longer.

Best regards

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02 Aug 2021 14:11 #10087 by Restrepo
Also, the customer tested other OPC DA clients such as Quick Client and OPC Explorer by Matrikon and they are getting data without any Access denied issues. The customer seems to think that this is isolated to only OPC QUick Client to he is not too convinced that this is a DCOM issue. Would you mind suggesting any type of looking our troubleshooting method with the toolkit to prove that this is a DCOM issue? Thank you in advance.

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02 Aug 2021 12:23 #10086 by Restrepo
Thank you for all the assistance so far. So, the customer decided to open up DCOM, but he still gets the access denied while other OPC DA clients can connect to the server. I tried to put the OPC Analyzer in the middle to see if we have any luck connecting to the Analyzer ProgID instead of the actual server but he keeps getting access denied.

Now, interestingly, running the OPC Data Client app as Admin yields a different error (See screenshot). Would this provide you with more clues on what could be happening here? The customer seems to think that this is an issue with the toolkit since he has been able to get every other OPC DA client to connect without any issue, so I would appreciate it if you could explain what could be the issue here. Thank you in advance.
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27 Jul 2021 06:49 #10054 by support
Hello.

The only remaining option is to re-check the DCOM configuration. It is possible that somewhat different setting might be needed for .NET-based clients, but I do not have more concrete hint. Attempt to set the security completely open to "everyone", and if it starts working, tighten it up. But I cannot think of anything else.

Best regards

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27 Jul 2021 03:02 #10053 by Restrepo
Hello Z,

Thank you for the suggestions. However, it seems like the setting is not changing the behavior. do you have any other suggestions? Attached, I will include the code (frmDACleint_UI.vb) just in case it helps. Please let me know if you need anything else. Thank you very much for your support.
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23 Jul 2021 08:20 #10036 by support
Hello.

I know that the issue is related to DCOM - basically, we sometimes require different settings from what other OPC clients need, due to internal implementation, plus the proper combination of these parameters - but unfortunately I do not have a concrete recommendation on how they should like like in particular situation.

Here is one more thing to test out:

Please have the customer put the following right after the creation of the EasyDAClient object (important: *before* any actual OPC operation is done) into the code:
client.InstanceParameters.EnableNativeClient = false;
(where 'client' is the easyDAClient object, the variable name can differ).

This switches parts of the internal implementation to a different code which should behave more closely to "traditional" OPC client. I am normally hesitant to suggest this, because there is a slight risk that some other behavior changes and something in the client's app gets broken.

Best regards

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22 Jul 2021 13:45 #10033 by Restrepo
Thank you for the suggestions.

Unfortunately, the customer tried all 8 combinations when changing the parameters suggested on the post you suggested and he still getting the same Access Denied issue.

Do you have any other suggestions that we could try so that we can borrow down the issue?

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21 Jul 2021 19:18 #10029 by support
Hello.

Can the customer please try the different settings of EasyDAClient.ClientParameters.UseCustomSecurity , TurnOffActivationSecurity and TurnOffCallSecurity as listed here?: www.opclabs.com/forum/connections-reconnections-com-dcom/124...-remote-machines-via-code#1392 .

Note that different combinations cannot be tried in the same run of the program.

Best regards

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21 Jul 2021 17:07 #10026 by Restrepo
Hello Z,

I am currently working with a customer that is encountering an Error whenever trying to connect to WinCC OPC DA server. Basically, in his code, he is subscribing to multiple tags but the application returns this error:

*7/20/2021 10:08:59 AM DA_Client1 Error Itemchanged-: System.UnauthorizedAccessException Access is denied. + The client method called was 'ItemChanged'.

So, I had him test with the EasyDA Client Demo and connectivity explorer and he is getting the same issue as you can see in the screenshots attached.

Now, the weird part is that he is able to communicate to that sam server using Matrikon OPC Explorer so I am not sure what is happening here. I did have the chance to read over this post in this forum > www.opclabs.com/forum/browsing/3226-error-access-is-denied-t...or-event-callback-invoked#9808 < But the customer is running the latest version and I am not sure he is using an appsettings.json in his application.

Do you have any ideas on what could be happening here? Please do let me know if you need anything else. Thank you in advance.

Customer's environment:

Microsoft Visual Studio Community 2019
Version 16.10.2
VisualStudio.16.Release/16.10.2+31410.357
Microsoft .NET Framework
Version 4.8.04084

OPC Data Client V 5.61.241.1
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