Recently, I found an interesting problem in reading data from OPC server using OPC version 2.0. I am using the KpOPC.dll. I could read tags but could not read values. However, I definitely could get values in my demo which aimed in debugging this problem. The only difference is that rapidscada is running based on window service but my demo is not. It’s so wired!
I emailed my demo to your gmail. I will apprecited it if you could give any advise!
I think the cause that the service and your app work by different users. Service works as system. Your app works as other user. Try changing the user of the service. See the end of the article http://rapidscada.org/connecting-devices-using-opc-standard/
Please write about the result.
Note. What do you think is OPC UA is actual for you?
Thanks so much for your nice reply!
I tried to follow the suggestions from that page step by step carefully. Neither solution worked. The ‘State’ in the SCADA-Communicator was ‘error’. I tried in 3 computers in win10, win7 and xp. None of them worked. It’s so wired.
I tried to test the OPC server using other OPC client. They worked well. It means the OPC server has no problem. As you know, in the last time, I wrote a demo to communicate with the OPC server using codes from kpopc. It did work well when I did not use window service.
Therefore, I think the problem should be related to the window service. Could somebody advise how to solve this problem?