Patent ID: 7693934

Claim:
A network system, comprising: a control point which transmits discovery packets to search for devices existing in a network, receive response messages thereto and control the devices existing in the network; and controlled devices, each of which receives notify messages transmitted from other controlled devices connected in the network, wherein each of the notify messages includes an operational state of the transmitting controlled device, generates, stores and manages a list of service information on the operational state of all controlled devices connected in the network, through the received notify messages, and searches and transmits service information on a controlled device requested by the control point to the control point, wherein the control point comprises a cache which stores information regarding devices on the network, wherein each controlled device generates a token, transfers the generated token to another controlled device, and manages the token, the token transferring comprising: checking, by the controlled device, the number of controlled devices in the list of controlled devices stored in the controlled device; if it is determined that the number of controlled devices in the list is more than two, transferring the token and the stored list of controlled devices to another controlled device; checking whether a response message is received from the other controlled device and operating a self-timer of the controlled device; and if the response message is received from the other controlled device, stopping the self-timer and operating a waiting timer of the controlled device; and if the response message is not received from the other controlled device; the controlled device deletes the other controlled device, which has not transmitted the response message, from the list of controlled devices; and the controlled device notifies a control point that the controlled device, which had not transmitted the response message, does not exist in the network.