COMMUNICATION DEVICE, COMMUNICATION METHOD, INTEGRATED CIRCUIT, AND PROGRAM

摘要

Provided is a terminal device a (405) including: a connection environment check unit (601); a determination purpose port mapping command unit (602) which issues a port mapping command to a lower layer NAT device a (404); a determination packet generation unit (603) which generates a determination packet which is source-routed; a determination packet transmitting unit (608) which transmits the determination packet; a determination packet receiving unit (609) which receives the determination packet transmitted from the determination packet transmitting unit (608), passing through the upper layer NAT device a (403) and the lower layer NAT device a (404), and arriving at the terminal device a (405); and a port number obtainment unit (615) which obtains a WAN-side port number of the lower layer NAT device a (404) indicated in the received determination packet.