Strange Error connecting to OPC server

[Orio]

Good Morning,
i met a strange behavior using datasocket to read items from a 3rd party OPC server. The same client code runs correctly (see the items, connect to server, acquire data values) on a (test)machine running under WinXP. On the other machine (XP too) i can browse correctly the remote items, but when i try to connect to them i receive the error
"The remote server can not connect to this machine (check local permissions)"
My big doubt resides in the fact that the two client machines have DCOM configured in the same way (same settings in dcomcnfg), i use the same network parameters (addresses, usernames and passwords). The environment i'm in doesn't have any NT domain, but both the server and the client machines are in the sa
me workgroup, and I log in client machines with the same username and password of the user that is logged on the server machine and runs the server application. In your opinion is there anything i missed or anything i can try? Am I so unlucky?

Thank you a lot for help.
Best regards.
Mattia Monarca.

[HeinerI]

For establishing a properly working remote connection to an OPC server under Windows NT operating systems you need to setup several things, the right settings under dcomcnfg are only one part of this procedure.
Because we do know that this is not a trivial task, we created a knowledgebase entry covering this issue.
Please follow the following link (which also contains some links to Microsofts Knowledgebase):
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/5c8a90cd57b279f286256c2c006f1eb4?OpenDocument

Regards,
Heinrich Illig
National Instruments

[HeinerI]

One thing more I would like to mention. Normaly you should have a NT server being available which acts as a domain server to which both machines are being hooked up, but we found out that if you don't have a domain server available and your both computers are in the same workgroup the connection to the remote server does work if on both computers the user is logged in with the same user name. We havn't fully tested this so far but maybe that's a quick workaround for you when you don't have a NT domain server available.

Regards,
Heinrich Illig
National Instruments

[Orio]

Thank you very much Heinrich for the quickness of your reply. I confirm you that using same user and password on both machines is a good tip if there are no domains.
I've tried changing registry permissions (SecurePipeServers and so on), including Everyone (without your helpfull documentation, developing also the simplest client would have been too difficult for me), but that doesn't result in a change of behavior. Do I have to perform the changes also to other registry entries (the ones in Microsoft's document)? If so in what way can i move, i.e. what changes have to be done first?

Thank you again.
Mattia Monarca

[HeinerI]

For the szenario where you don't have a domain server available we found out that's not necessary to make any changes in the registries of the computers and it was also not necessary to apply any dcom configurations on this computers. The only thing we did was setting up 2 computers in the same way with Windows 2000 with different computer names, same workgroup and same user with same password. After connecting this both computers via Ethernet and after installing our OPC server on one machine we were able to connect to the server and having access to it's data. On both computers we did a standard installation of Windows 2000 (SP2) but nothing special. Hope this helps, otherwise please check your system on which it differs from a standard instal
lation or if your OPC server needs anything special.

Regards,
Heinrich Illig
National Instruments

[Orio]

Your words comfort me and suggest on reinstall all the software on the client machine (the one that doesn't work). I'm sorry I'm filling you with my questions, but I'd like to know also if in Windows XP there is something different from Windows 2000. Another thing I don't understand is why sometimes I'm asked to insert Office2000 CD-ROM when I'm using SelectUrl().
You're really helping me a lot on finding what's wrong.
Hope someday i'll be useful too!! 🙂

Regards,
Mattia Monarca.

[HeinerI]

Sorry, but this is beyond of the scope what NI's support can offer but I'm sure you can get help from Microsofts Knowledgebase because the questions you do have now are more related to their products and technologies.

Regards,
Heinrich Illig
National Instruments