Windows service raising event in client app

VS 2005/.net framework 2.0

I have a windows service on a server which monitors a folder for changes. When a file is added or deleted its file name is added/removed from a sql server database table.

I also have a bunch of windows client applications delivered from the same server using click once deployment. The applications basically present the users with a list of files currently in the folder on the server. They just get a list from sql of the files and present them to the user.

The problem I have is that I am not sure how I can get the windows service to raise an event in the client applications telling them that they must requery. All comms must be via port 80.

Any Ideas folks ?


Thanks in Advance :-)