How to achieve callbacks in WCF service?

Question

I have to create a WCF service that handles following tasks:

1. Register the notification sent from multiple client through WCF service.
2. The WCF service in turn sends ( Callback) the notification to the multiple client.

The WCF service also want to listen a datachange notification from another database server.

Can a WCF service is treated as a Listener that listen and send notifications for each request.

Answer 1

If I understood correctly, what you need is duplex services.

Answer 2

There is a Callback Contract, msdn , blog post about it