your job can be done by either web service or WCF.
and actually wcf is a great extension of web service in .net 3 and higher
I recommend WCF because it has these advantages over web service:
http://www.techbubbles.com/wcf/wcf-vs-aspnet-web-services/
http://geekswithblogs.net/khanna/archive/2006/01/06/65067.aspx