An electronic apparatus includes a communication device that communicates with a mobile device and a plurality of devices via a network. The mobile device is wirelessly connectable to the network. The electronic apparatus further includes a control unit configured to determine whether the mobile device is disconnected from the network, and a message sending unit configured to send an alarm message to one of the devices by communication between the one of the devices and the communication device when the mobile device is disconnected from the network, the one of the devices being currently powered on.