An HTTP relay server determines whether a communication partner device is a supporting device or a supported device, using a device management table. Further, the HTTP relay server determines a state of a state (used or unused) of a URI indicating an area where support data are temporarily stored, and a device using the URI (device ID), using the URI management table. When access (communication request) is received from an image forming apparatus, the HTTP relay server assigns the image forming apparatus to an unused URI. Further, when access (communication request) is received from an operator PC, the HTTP relay server assigns the operator PC to an URI used by the supported device.