COMMUNICATION APPARATUS, COMMUNICATION METHOD AND COMMUNICATION SYSTEM

摘要

A communication apparatus (10) sets [SP1] as a destination port number and transmits three address information research requests (1-3), in which respective different [LP1]-[LP3] are set as transmitting source port numbers, to a server (001). Between the address information research requests (1 and 3), the communication apparatus (10) also transmits a P2P communication preparation packet, in which one of [LP1]-[LP3] is set as a transmitting source port number, to a destination different from the server (001). The communication apparatus (10) determines, based on port numbers [GP11], [GP12] and [GP14] of a router (101) notified by address information research responses (1-3), the NAT characteristic of the router (101).