Patent ID: 8024593

Claim:
A communication device for communicating via a network to provide a service to another communication device on the network, the communication device comprising: a main processing unit operable to process a main service to be provided to the other communication device; a communication processing unit operable to transmit and receive request information and response information corresponding to the request information with the other communication device via the network; and a power supply unit operable to stop supplying power to said main processing unit while in a state of being able to supply the power again and operable to supply the power to said communication processing unit, wherein said communication processing unit comprises: a memory operable to store information required to create an alive packet which is transmitted periodically at a predetermined time and which indicates that the communication device is in a state of being able to provide the service, the required information including address information of the communication device, identification information of the communication device, and service information for the service provided by said main processing unit; an alive packet transmitting unit operable to (i) read out, from said memory, at least the address information of the communication device and the service information, (ii) create the alive packet including the read out address information and service information, and (iii) transmit the created alive packet; a response possibility determining unit operable to determine whether or not said communication processing unit is individually able to respond to the request information received from the other communication device which has received the alive packet; a response unit operable to create the response information and to transmit the response information to the other communication device, when the determination indicates that the response is possible; a power supply controlling unit operable to start said main processing unit, to control said power supply unit, and to supply the power to said main processing unit, when the determination indicates that the response is not possible; and an address management unit operable to store information indicating an address of the communication device and a term of validity of the address, and, when a period until expiration of the term of validity reaches a predetermined time, to start said main processing unit via said power supply controlling unit to supply the power to said main processing unit, and to cause said main processing unit to execute an update processing of the address, wherein said alive packet transmitting unit creates and transmits the alive packet while said main processing unit is in a condition of not yet having power to provide a main service.