800xA 5.1: error when adding a remote OPC node ("could not access the specified computer!") - firewall isse?

See the attached screenshot. I get the following error when trying to add a remote OPC server:

"Could not access the specified computer! Error: The network path was not found. (0x80070035)".

There is a firewall between the OPC node and the connectivity server, and I think this is the reason for the error.

I need to know exactly what services/ports need to be allowed in the firewall for this to work. I know port TCP 135 for DCOM/OPC must be open, but what else?

(I have already tested the OPC connection between the connectivity server and the remote OPC server node using a third-party OPC client and it does work.)


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asked 7 months ago



Hello, for testing purpose better you can make transparent setting in firewall. It means, open all ports of Firewall and start communicating. Once this is okay, then do the setting only for Port No 135.


answered 7 months ago


By sekeze on 6/28/2017 | Like (0) | Report

Unfortunately I cannot do that. I have no access to the firewall configuration. I can apply for IT to open certain ports/services for me, but I'd need to know exactly which ports/services to apply for.

By ershivkumar2002 on 6/28/2017 | Like (0) | Report

Firewall engineer is the right person for configuration.

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This is the downside with DCOM.

Remember that the outgoing connection from System 800xA will be made from a process called AdvDsOPCConnector.exe running as a background service. A background service has less features enabled (eg no GUI possible) than a process running in the foreground, eg an OPC test client. OPC servers having a splash screen need to disable it, or they will hang when launched from the 800xA DA Connector.

For asynchronous DCOM, please note that OPC server must be permitted to post callbacks to the client (=AdvDsOPCConnector.exe).

See also attachments to my answer on this thread (http://www402.abbext.com/800xa-opc-client-q8372173.aspx). This is opposite direction, but the DCOM restrictions apply here as well.

Ultimately, an OPC Tunneler might be the easiest way out.

Stefan Stromqvist   

answered 7 months ago


By sekeze on 6/29/2017 | Like (0) | Report

Actually, for once I don't think this is a DCOM issue. I've got all the DCOM settings covered. Using two user accounts on both sides, I've got both synchronous/asynchronous read/write working between a third-party OPC client and the remote OPC node. I've sat the correct DCOM settings on the OPC DA connector.

I think the problem is that when I enter the IP address of a remote note in the Special Configuration tab of a OPC da connector service provider, it uses a port or service that disallowed in the firewall. Perhaps it uses "Client for microsoft networks", NetBIOS, ICMP or something else. I think the reason it works with the third-party OPC client because it *only* uses port tcp 135, which is the only port open in the firewall. Googling the error code 0x80070035 leads me to believe this.

By Stefan Stromqvist on 6/29/2017 | Like (0) | Report

Turn on firewall logging and see if something is dropped. The connector should be exempted from firewall by default config rules.

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Its free and excellent for solving OPC security issues.

Rob Lyon   

answered 7 months ago


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