A utility for enabling real-time, point-to-point communications over computer networks between users having dynamically assigned Internet Protocol addresses includes the ability to identify incoming communications, and, based on the identity of the incoming communication, selectively responding. In one embodiment, an information profile contained within an incoming signal is compared to a plurality of information profiles contained within the personal directory of a user, and, if a match occurs, the notification signal associated with the matched profile is generated. In an alternative embodiment, the information profile contained within the incoming communication includes an identifier of a notification signal which is used to select from a number of predefined notification signals resident within the user's private directory.