OPC Error: Opto22 Server w/ Datasocket Client

[David Moerman]

I have a problem connecting to the Opto22 OPC Server using Datasocket 4.0 & LabVIEW 6.1. I can browse the server just fine, which gives me the following URL:
"opc://localhost/Opto22.OpcServer.2/[b3000|tcp|192.168.2.222,2001]EU.0".
But when I try to open it using the URL provided, I get the error "(-2147467259) Can't add item to OPC Group. Error Code 0x80004005". When I check the Opto22 OPC Server it displays the following log:
"
AddGroup: tg
ValidateItems - count: 1
Added 1 items to group tg
CreateEnumerator - Group: tg Items: 1
RemoveItems from group tg - count: 1
RemoveGroup: tg
"
The funny thing is that I can connect to this OPC server just fine using LabVIEW DSC tags, but I want to prove to my client that I
can use Datasocket as well. In addition, I have successfully connected to the OPC items via the Server Explorer. Can anybody guess why my Datasocket URL won't work?

[Mike S. @NI]

David,

There are 3 ways LabVIEW can use Datasocket to connect to OPC servers:

1. Front panel connections
2. LabVIEW 6 functions (DSWrite and DSRead)
3. LabVIEW 5 VIs (see Multiple OPC Item Monitor.vi in the shipping OPC examples)

Which of these methods are you using? National Instruments currently recommends the third one. Please try the other methods, if you haven't already, and let me know the results.

Regards,
Michael Shasteen
Applications Engineering
National Instruments

[David Moerman]

I have attempted all 3 ways, with exactly the same results.
-Dave

[Mike S. @NI]

Sorry for the tardiness of my response. Does the server use synchronous or asynchronous communication?

[David Moerman]

Uses asynchronous

[Mike S. @NI]

This is a known issue that R&D is currently investigating. Your best bet for now is to use LabVIEW DSC with asynchronous OPC servers.