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network opc access

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12 Jan 2011 08:29 #189 by support
Replied by support on topic Re: network opc access
From: Zbynek Zahradnik
Sent: Wednesday, January 12, 2011 9:26 AM
To: .....
Subject: RE: remote OPC


Dear Sir,

Thank you for your call and email.


It is a bit difficult to troubleshoot things like this through email, as there are many steps and things to be checked, so it may take quite a lot emails to get to the results. That's why we recommend to study the available materials (such as OPC/DCOM configuration guides), and attempt to follow the steps outlined there.

Anyway, I will try to help you out. Can you please first answer:


1. When and where are you getting "Access denied". Is it an exception thrown by a call to a method on EasyDAClient object, such as ReadItemValue?


2. Have you tried some other OPC client on the same computer as your application, to connect to the target server? If so, which client software it was? Is it also giving you a similar error, or does it work well?


3. Which version of IIS is used to run your ASP.NET application? This is important to establish the identity under which the OPC calls are made. In older IIS versions, which Isolation Level (Low/Medium/High) is used? In newer IIS versions, which App Pool is your application assigned to? What is the user account this App Pool is running under?


Thank you in advance
Zbynek Zahradnik, OPC Labs

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12 Jan 2011 08:28 #188 by support
Replied by support on topic Re: network opc access
From: ...
Sent: Monday, January 10, 2011 1:54 PM
To: Zbynek Zahradnik
Subject: remote OPC

hi
i need a training of remote OPC, i'm getting access denied i use vb.net asp.net for this

......

thank you. Submitted By: a.

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28 Nov 2010 11:55 #146 by support
Replied by support on topic Re: network opc access
In order to access remote OPC server, the VB.NET code can remain mostly as it is for local servers, with the only change in the first argument to most method calls: An empty string ("") denotes a local machine, while anything else specifies an OPC server on that remote machine. The string can contain anything that the operating system recognizes as computer name - among others, a WINS name (e.g. "OPC-MACHINE-1"), a DNS name (e.g. "opc-machine-1.factory.local"), or a numeric IP address (e.g. "192.168.1.23").
The code to read a single value may then look like this:

' Create EasyOPC-DA component
Dim EasyDAClient As New OpcLabs.EasyOpc.DataAccess.EasyDAClient

' Read item value and display it in a message box
MessageBox.Show(EasyDAClient.ReadItemValue("OPC-MACHINE-1", "OPCLabs.KitServer.2", "Demo.Single"))


If you are using other method calls, the code change would be similar; send me relevant pieces of your code if you are unsure where and howto make the modifications, and I will suggest the necessary changes.
It also appears from your question that you may have run into some kind of permission problem. Let me state that this is VERY common with remote OPC access, which is based on DCOM and requires it be configured properly. The correct configuration depends on your requirements, and needs rather elaborate description. For this reason, I refer you to ready-made materials that were written on the subject, such as these:

support.softwaretoolbox.com/cg...
www.softwaretoolbox.com/xpsp2/...
<a href="opcfoundation.org/DownloadFile.aspx?CM=3&RI=326&CU=1" target="_blank" rel="nofollow">opcfoundation.org/DownloadFile...

Please follow the instructions; if you still have problems, let me know and indicate what you have done and what error are you getting.
Best regards,
Zbynek Zahradnik
P.S. A somewhat related thread in these forums: www.opclabs.com/Support/Online...

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28 Nov 2010 11:34 #145 by support
network opc access was created by support
From: contact-feedback
Sent: Friday, November 26, 2010 5:28 PM
To: Zbynek Zahradnik
Subject: opc for network permission problem - vb.net sample

hi

plz send me setting for network opc access from other PC

opc for network permission problem - vb.net sample for network access as well.

.....

thank you
a.

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