You need remoting / WCF   or  a sql server and notification services i use
this in my current project as i wanted this to function at all times (
without Admin intervention to open the needed ports )

my Client just subscribes to a dataset where the windows service is writing
its events in , on every event the client is notified by notification
services and can thus synchronize the messages that were written

if you can not set up notfication services there is also the posibility to
poll the database once in a while to see if there are changes

HTH

Michel