Patent ID: 7441002

Claim:
A method of establishing a data connection between a first of a plurality of computers on a network and a second of said plurality of computers, each of the first computers being logically associated with a respective user, the method comprising: storing in a directory database entries comprising fields for at least a network address of a computer currently associated with each user, and a unique identifier for each user; storing at each of the computers a respective data item comprising a field containing the respective unique identifier for the logically associated user; responding at a server to receipt of a message from a first user at the first computer indicative of a desired data communication with the second computer and containing identifying data for the second user, the identifying data corresponding to a field of said directory entries, by accessing the directory database in accordance with said identifying data, and, if a unique entry is found for the second user, retrieving the network address of said unique entry, sending from said server to the second computer at said retrieved network address and to the first computer at the source network address of said received message, a respective message requesting a return message containing the field of the respective stored data item; responding to receipt at the server of each respective return message by accessing the directory database in accordance with content of the field of the respective return message, and checking that only a single entry is returned by this accessing step if only a respective single entry is returned for both of said return messages, sending one of the first and second computers a message instructing said one computer to make a data call and containing for a destination address for said data call the network address of the other one of the first and second computers.