If the OPC client application is a COM object and does not initialize DCOM security programmatically, then the DCOMCNFG utility must be used to specify the Access Permissions and the Authentication Level. This is required for authenticating callbacks into the client by the OPC server. DCOM Security on the OPC client computer node must not only authenticate the user identify of the OPC server but also must determine if the OPC Server is allowed to make calls on client owned objects. Callbacks are invoked by the OPC server to provide subscription updates and completion notifications for asynchronous read and write operations.
If the OPC client application is not a COM object (i.e. the OPC client application is not listed in DCOMCNFG), then the DCOM security settings for Default Access Permissions and Default Authentication Level are applied.
Step 1.2. GagePortOPC Client Setup Steps.