A complex server application based on the COM technology and developed using MS Visual C++ 6.0 and the ATL library.
This server deals with the management of an event list. Events are generated as a consequence of a field variable change of state. Field variables are handled by an OPC data access server to whom ES connects and subscribes to so as to get changes of state.
As you can see in the UML diagram, the event server is made of three COM components:
- Event Server: This is the main component. It loads the configuration and exposes interfaces for registration and subscription. Clients use these interfaces to begin a connection.
- Subscription: This component exposes interfaces for event management to the client.
- OPC handler: This component deals with the communication between the Event Server and the OPC Data Access server.
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