Applies To:
  • CitectSCADA 5.xx

I am running the Citect OPC client driver connecting to a remote OPC server on another PC, Citect reads the values on startup but never updates those values after startup.  What could be the problem? 

This is most likely a DCOM security issue.  DCOM security must be opened up on both the server and the client PC.  On startup the OPC client (Citect) will request data from the OPC server and if the OPC server PC has security set which allows access, the server will respond with the data.  

Since the OPC client PC initiated the read request the client is expecting a response and reads the data from the server but after the initial startup it is the OPC server which notifies the client of any change in data.  Keeping that in mind, if the OPC client machine is not configured to allow access from the OPC server then it will never allow any change in data notifications through and will never update the tag values.

You can modify DCOM security in the dcomcnfg.exe program found in the WinNT\System32 directory.