Cannot Connect to SVE OPC Server Across LAN

[Wes_Ramm1]

Good morning everyone, I spent a HELLISH day yesterday trying to sort this problem out, and screwed up the registry on my own PC.  So, any help would be GREATLY appreciated.

I am deploying a LV 8.20 executable for a client.  The Executable has 3 Shared Variables, and I am using the 'deploy library' command during initialization to force my executable to act as an OPC server.  From my local PC I can use the NI Server Explorer, and a couple of third-party OPC client apps to see that I am, indeed, publishing the data as an OPC server.

The problem comes when I try to use another PC on the LAN to act as an OPC server to 'see' the published data from the first PC.

Network Topology:  Windows XP Pro boxes on a linksys wireless router.  I can successfully connect PC to PC, and they are both (I am starting with two PCs) on the same workgroup, which happens to be 'MSHOME' here at my client site.

When I try to connect to the OPC server with a second PC, I get a message like 'Connection Refused, insure that both PCs are on the network, that remote administration is active, and that remote registry services are enabled.'

I have found quite a  few forum posts with people asking the very same question that I am, but no one seemed to have a definitive answer to how to get two PCs to share OPC info on a LAN.  Most of the posts I have found point you to posts for enabling DCOM on the PCs.  I have followed all the instructions that I could find, changing registry settings, turning on and off different Windows services, setting permissions, etc. I have gone so far into these settings (without any really definitive process to follow) so far, that I have managed to render my PC unable to serve as an OPC server any longer.  In fact, once I am done with this post I have to repair my OS.

All the documents and forum posts I can find are a little older, and refer to Win 98, ME, etc. 

Has ANYONE gone through this process of getting a client PC to talk to a LV 8.20 SVE OPC Server through a LAN?  The instructions and guidance I have found on the web were nothing short of diabolical. 

Any help would be appreciated.

Wes

[Lorielle P]

Hi Wes.

If I understand your application, you have an executable running as an OPC server and encounter the error message when trying to connect to the server from a client computer on the same network.  Some more information may help to clear up the picture.  How are you accessing the data on the client computer (LabVIEW development VI, LabVIEW DSC, TCP/IP, DataSocket)?  And the variables are network-published?  Are you using unique static IPs or dynamic IPs?

Hopefully, with this additional information, we'll be able to pinpoint what may be the culprit.

[Wes_Ramm1]

Lorielle,

It gets better.  In trying to follow the instructions to get DCOM applications to communicate with each other over Windows networks, I managed to screw up my own PC so badly that I cannot even connect to the OPC server locally.  That is another issue I have to deal with.

Here is the thing.  I have three shared variables, which are network published, that I intend to use to 'serve' three parameters to an OPC client application living on another computer across the network. 

I was testing my configuration by using the NI Server Explorer application on the remote PC.  At one point, I could see the OPC tags being published on the Local PC using the Server Explorer, but as I said, I am no longer able to do so. 

I have found a number of white papers and articles (not at NI) as to how to configure PCs to be able to share DCOM over a network.  This is obviously not an easy task, and I thought that it was going to be a slam dunk. 

Does NI have any guidelines that describe the exact, complete methodology that describes how to configure Windows PC's to communicate via DCOM?  I would think that you must, as the OPC server that is a part of the SVE relies on this technology.  To date, however, I have not been able to find any newer documents for this purpose.

Any help is appreciated.

Wes

[Xaq]

Wes-

There are a few places where you can get the information for configuring DCOM setting in Windows. This KB walks you through all the correct registry settings for remote access with Windows 2k/XP:

http://ae.natinst.com/operations/ae/public.nsf/web/searchinternal/6DBB89FA247C541C862570F1006A3E87?OpenDocument

And this document from the OPC Foundation discusses permissions and some firewall setting you may have to configure in Windows XP SP2:
http://www.opcfoundation.org/Archive/72e9fbfa-6a89-4ef2-9b6d-3f746fd7eb05/Using%20OPC%20via%20DCOM%20with%20XP%20SP2.pdf

Xaq

[Wes_Ramm1]

Xaq,
Thanks, I'll give it a shot and post back here my progress.

Thanks everyone for your time and help.

Wes

[Wes_Ramm1]

Ack, the first link does not work.

[TLE]

I was fighting the exact same battle.  Tech support told me that Windows XP security makes OPC across the network very difficult.  However, there is an acceptable work around (at least for us).  Datasockets work fine over a Windows XP network.  Create an application on the server computer that writes data to a shared variable(s).  On the client computer, create an application that reads the shared variable on the server using datasockets.  The client application can then write this data to its own local shared variable.  As a result, any OPC client on the client computer can get at the OPC data.

Not the most elegant solution but it should work.

[Xaq]

Wes,

The first link from my post above is not available on the web, you can disregard it. Keep us posted.