A computer performs a control including (1) receiving a request for monitoring a station to-be-handled which is a communication apparatus different from a pertinent station including the computer, (2) transmitting a request for a response based on the station to-be-handled, to the station to-be-handled at a predetermined time interval, on the basis of the monitoring request, and (3) transmitting a message expressing that the station to-be-handled will be detached from a network, to the network if the response to the response request was not received within a predetermined wait time.