Abstract: A wireless communication node device is provided. The node device includes a network adaptor configured to perform short-range wireless communication, a channel manager configured to receive channel setting information comprising information about channel member nodes through the network adaptor, and to store the received channel setting information, a channel state manager configured to update a channel state table which indicates that the node device is connected to another node device, in response to the node device being connected to the other node device through the network adaptor, and to propagate the updated connection state table via the network adaptor, and an alarm controller configured to verify a connection state between the channel member nodes by analyzing the connection state table, and to generate an alarm control signal based on the verified connection state.

Abstract: A wireless communication node device is provided. The node device includes a network adaptor configured to perform short-range wireless communication, a channel manager configured to receive channel setting information comprising information about channel member nodes through the network adaptor, and to store the received channel setting information, a channel state manager configured to update a channel state table which indicates that the node device is connected to another node device, in response to the node device being connected to the other node device through the network adaptor, and to propagate the updated connection state table via the network adaptor, and an alarm controller configured to verify a connection state between the channel member nodes by analyzing the connection state table, and to generate an alarm control signal based on the verified connection state.

Abstract: Provided are a file management server and a system and method for managing a file. The system includes a user terminal configured to request a unique file number for a file when the file is generated, and a file management server configured to generate the unique file number corresponding to the file and transmit the unique file number to the user terminal upon the request, track a usage history of the file through the unique file number, and manage a right to use the file according to a user status related to the file when a user terminal inquires about whether the file is usable.