The first part can be achieved by maintaining a list of what you have subscribed to on your side (in one common storage), as it is completely under your control.

Not sure what you mean by the second part. If you refer to some kind of error handling, then be careful with that, and read the documentation first. In QuickOPC, a "subscribe" call indicates a permanent intent to become and stay subscribed - valid until a corresponding "unsubscribe" is called. In case of any errors, you will still receive a valid subscription handle. You just get an error notification (event or callback), and after a configurable period, QuickOPC will attempt to subscribe again - and so on. This approach automatically handles reconnections in case of errors caused e.g. by temporary network or server failures, server restarts, transient server misconfigurations, etc.

Best regards

Not really, but please describe your use case (what are you trying to achieve), and I should be able to help you. Normally, such method should not be needed.

Best regards