Translator for ip networks, network system using the translator, and ip network coupling method therefor

A terminal device for receiving and/or transmitting Internet Protocol Version 4 (IPv4) packet through a network, the terminal device comprising:

• a processing unit for performing an Internet Protocol Version 6 (IPv6) application program;
• an address translation information reception unit for receiving, from another device having been connected to the terminal device through the network, an address translation information showing corresponded relationship between an IPv6 address and an IPv4 address;
• a memory unit for storing both the IPv6 address and the IPv4 address, having the address translation information which has been received at the address translation information reception unit, with the corresponded relationship;
• and
• a translating unit for, in response to a reception of the IPv4 packet through the network, extracting from the memory unit an IPv6 address which has been stored in the memory unit with being corresponded to an IPv4 address having been included within the IPv4 packet as a source address, for generating an IPv6 packet by translating the IPv4 packet into the IPv6 address for which the IPv4 address as the source address has been extracted, and for making the IPv6 application program, to be performed by the processing unit, process the generated IPv6 packet.