A server may store one or more accounts. Each account may be associated with an authentication code and a total number of information devices that are allowed to be registered. The authentication codes may be provided to users for registering information devices. The information device may transmit a connection request, including an entered authentication code, to a server. Upon receiving the connection request, the server may determine whether to register the particular information device. The server may determine whether the information device is allowed to be registered based on registerable information, which is associated with an account that is associated with the received authentication code and which represents a remaining number of information devices that are allowed to be registered using the associated authentication code. If the information device is allowed to be registered, the server may send authentication information to the information device, so it may transmit state information.