M
I am seeing an interesting problem I wonder if anyone can explain. I have tried this with with several servers and several clients from various vendors and all show the same behaviour.
I configure an OPC server with at least two tags.
I select an OPC client that can send multiple items in a write operation at once. Many clients send only individual write items/data, one at a time.
I configure the client with a group and add two items for the two server tags. Add the items as VT_BSTR. (It does seem to matter whether tags in the Server are VT_BSTR or not.)
Now set the data to send to two different VT_BSTR values and trigger the operation. 9 times out of 10 the VT_BSTR data received at the server is the same for both items. (I say 9 out of 10 because I think I saw it work once or twice but I am not sure with the clients I am using that they always send both peices of data - they may only send one's changed? At any rate it happens consistently).
I only see this happen if all data is VT_BSTR.
Can anyone help me explain this or tell me that they do not see this? Maybe its a OS configuration problem?
Thanks for any suggestions/assistance.
Mike
-----------------------------------------------------------------------------
From: Michael Dannhardt, DASTEC Corporation
Address: 457A Carlisle Drive;
Herndon, VA 20170 USA
Tel: 703 709 0515
Fax: 703 709 0985
E-mail: [email protected]
Web: http://www.dastec.com
-----------------------------------------------------------------------------
I configure an OPC server with at least two tags.
I select an OPC client that can send multiple items in a write operation at once. Many clients send only individual write items/data, one at a time.
I configure the client with a group and add two items for the two server tags. Add the items as VT_BSTR. (It does seem to matter whether tags in the Server are VT_BSTR or not.)
Now set the data to send to two different VT_BSTR values and trigger the operation. 9 times out of 10 the VT_BSTR data received at the server is the same for both items. (I say 9 out of 10 because I think I saw it work once or twice but I am not sure with the clients I am using that they always send both peices of data - they may only send one's changed? At any rate it happens consistently).
I only see this happen if all data is VT_BSTR.
Can anyone help me explain this or tell me that they do not see this? Maybe its a OS configuration problem?
Thanks for any suggestions/assistance.
Mike
-----------------------------------------------------------------------------
From: Michael Dannhardt, DASTEC Corporation
Address: 457A Carlisle Drive;
Herndon, VA 20170 USA
Tel: 703 709 0515
Fax: 703 709 0985
E-mail: [email protected]
Web: http://www.dastec.com
-----------------------------------------------------------------------------