A command processing apparatus includes a CPU (28). The CPU (28) determines whether or not a router (16) is compliant with UPnP, and issues a port releasing request to the router (16) when the determination result is affirmative. Thus, a specific port is released. Next, destination information including an identifier of the specific port is requested to be sent to a server (14). The destination information is sent to the server (14) by the router (16), and the server (14) sends a command to the specific port on the basis of the identifier included in the destination information. When the determination result is negative, an information send request is repeatedly issued. Every issuance, destination information including an identifier of an arbitrary port (response wait port) is sent to the server (14) by the router (16), and the response wait port is temporarily released. The server (14) outputs a command to the response wait port on the basis of the identifier included in the destination information.