A transfer unit transfers a message between a network and an external terminal. An input unit inputs a user ID for identifying a user. A generating unit generates a registration message requesting a registration of address information of the user. A transmitting unit transmits the registration message to a server. A receiving unit receives a response message including registration information and connection information from the server. When the connection information indicates a permission of a connection of the external terminal to the network, a control unit controls the transfer unit to transfer the message between the network and the external terminal.