In a conventional system, an eventing method and status inquiry method based on one-to-one communication are not suitable for notifying many unspecified network-connected hosts of the status of an apparatus in accordance with the WSD and UPnP protocols. A multicast packet capable of notifying many unspecified apparatuses of the status using one packet cannot transmit statuses other than connection and disconnection of an apparatus. To solve these problems, when the status of an apparatus changes, an identifier which is contained in a multicast packet and indicates the apparatus itself is sent after being replaced in accordance with the apparatus status without changing a format defined by a standard protocol. Upon receiving the packet, an apparatus determines, from the identifier contained in the multicast packet, whether to acquire information of the apparatus.