IP TELEPHONE SERVER, IP TELEPHONE CLIENT, METHOD AND PROGRAM FOR ESTABLISHING SESSION

摘要

PROBLEM TO BE SOLVED: To provide an IP telephone system which enables even a PC or the like having only a non-fixed IP address to use IP telephone. SOLUTION: An IP telephone client A transmits a calling control packet including the IP telephone address of an IP telephone client B. When receiving this packet, an IP telephone server A performs procedures for holding the non- fixed IP address of the client A till the end of IP telephone and transmits the packet to an IP telephone server B on the client B side. When receiving it, the server B performs procedures for holding the non-fixed IP address of the client B till the end of IP telephone and transmits the packet to the client B. The client B informs a user of incoming in a prescribed form when receiving it and transmits a response packet to the calling control packet to the client A when being instructed to respond to the incoming by the user.