How to make callbacks in a WCF service?

Question

I need to create a WCF service that handles the following tasks:

• Register a notification sent from several clients through the WCF service.
• The WCF service, in turn, sends a (callback) notification to multiple clients.

The WCF service also wants to listen for a notification with data from another database server.

Whether the WCF service can be treated as a listener that listens and sends notifications for each request.

Answer 1

There is a callback agreement, msdn , blog post about it

Answer 2

, .