opc dcom access denied

[Dave@Xerox]

I am connecting with Datasockets to a remote NI OPC server. Everything is working fine while the server and client computers are logged in under the same accounts (we are in a domain).

As soon as they are logged in under different accounts I get the old "Access to launch this server is denied. Please check the security settings for the server in dcomcnfg.exe."

Both accounts I am using are domain admins ... so they have admin priviliges on both machines. This will not always be the case but it is for now.

I have gone into dcomcnfg on both the client and the server and given "Everyone" full permissions on every DCOM object that appears to apply. Everyone says "Go into dcomcnfg and fix the security" but nobody says what object to fix.

Any help would be appreciated ... having everyone log in under the same account is not an option.

Dave

[StephenB]

Hi Dave,

Attached is the DCOM settings document that has awesome instructions and information about how to open up OPC Server. Hopefully this provides guidance and helps out.

[Dave@Xerox]

Appreciated Stephen ... I will give it a try and get back to you.

[Dave@Xerox]

Well I have opened up permissions to everyone and their brother for the "My Computer" object, the "NI OPC Servers" object and the OpcEnum object. Still have the same error.

One error on the NI OPC server that I see in the log is "Unable to load driver DLL 'C:\Program Files\National Instruments\Shared\NI OPC Servers\drivers\dataforth_isolynx_u.dll'"

I checked the folder and the dll is there. I try to register the dll with regsrv32 and I get Load Library Failed. The specified module could not be found.

I don't know if this dll is related as the server works fine if I log into the same account as the client.

Dave

[StephenB]

Hi Dave,

That dataforth dll is for a specific thing that doesn't have anything to with the dcom settings. Unfortunatly that driver is included with our newest version of our OPC server even though it is not compatible and this is a bug we have identified.

So did you go to my computer -> properties -> com security -> launch and activation permissions -> edit permissions

And from there give "Everyone"  all permissions.

You did this and are still having the problem? 

[Dave@Xerox]

Hi Stephen,

I have gone into the dcomcnfg.exe and applied these settings for 'Everyone', for 'Domain Users', and for 'Anonymous Logon'. I did this both at the My Computer object and in every OPC or DCOM object that seemed to apply (specifically noted above). I have restarted the services and rebooted the computers.

I am really stumped on this one ... the document you sent seems to have hit the issue right on but the solutions seem to have no effect.

[StephenB]

Hi Dave,

Unfortunately this is where things get complicated. Since we did not make DCOM (Microsoft did) or define it, its hard for us to figure out exactly what might be the problem here. Usually in situations like this, there is just a setting somewhere set wrong. One thing we can try is having the Variable engine service on the client machine logged in as the same user account as the server machine, regardless of what the current windows user is. For example, the server user name is 'bob' and the client user name is 'mark' but the variable engine service running on the client is logged on as 'bob'.

We can change this setting by going Start -> Run -> Services.msc -> National Instruments Variable Engine -> Properties -> Log On

And change it to use the same account as the server.

Let me know how that works. 

[Dave@Xerox]

Thanks for the effort Stephen. This last test was unsuccessful as well.

I am building a Windows Server 2003 box and I am going to give that a try.

Dave 

[Dave@Xerox · Accepted solution]

I had the same issues with Server 2003. So I am back to my original XP install.

But it seems I have found a solution: 

I noticed one option in the OPC server options which seems to have resolved my issues. Under the  "OPC Settings" tab there is an option for "Use DCOM configuration utility to set security" ... this is on by default. Unchecking this box and restarting the service seems to have done the trick.