Patent ID: 7864800

Claim:
A communication system comprising: a primary device connected to a primary network; a secondary device connected to a secondary network; and an address conversion device that converts address information of communication data transmitted from either the primary device or the secondary device to the other device, into address information corresponding to a network of the other device, and in which the secondary device stores the address information of the secondary device, in a storage area for the application data in the communication data, and transmits the address information to the primary device, wherein an auxiliary device is provided to handle communication between the address conversion device, the primary device and the secondary device, wherein the secondary device sends a request to the auxiliary device for address-conversion information, the auxiliary device: generates communication data for acquiring address-conversion information, the communication data including: an address of the secondary device in the secondary network as a sender address, and an address of the primary device in the primary network as a destination address; transmits the communication data for acquiring address-conversion information to the address conversion device, through a secondary device side interface thereof; and receives converted communication data for acquiring address-conversion information from the address conversion device, through the primary device side interface thereof; and acquires sender address information of the secondary device after conversion by the address conversion device; responds to the secondary device with the sender address information of the secondary device thus acquired; the secondary device stores the address information thus responded from the auxiliary device in the storage area for the application data in the communication data, and transmits the address to the primary device.