An agent device is connected with one or more image-forming devices in a local network having a firewall provided therein. A management device carries out remote management of the image-forming devices in the local network through the Internet. The agent device includes a command receiving unit which starts connection with the management device and receives a management command from the management device via the firewall, the command being sent by the management device in response to the connection. An image-forming-device communication unit receives device-state information of a corresponding one of the image-forming devices according to the management command. A command response transmitting unit transmits the device-state information to the management device through the Internet.