MVC to have a back-end service as messaging alarm [on hold]

How do I create a back-end service that able to send the message even none of a user access into the MVC web?

I dont want it to be done on another stand-alone application.

I had done the internal messaging function. Which is just a basic read-write database then post to user.

What I attempting to do is:

Example Scenario: Every 5 minutes, the back-end service will send an alarm message to all user.

All I know about MVC is only able to perform the action while one of the user is accessing to the web. I would like to create the back-end service which will running at behind and send internal message every 5 minutes even no user is accessing into the web.

I totally have no idea where to start with. Any Idea?