A user interface device for specifying network connection in a straightforward manner between information apparatus is provided. When a user wishes to connect two apparatuses, connection buttons on each apparatus are pressed down at the same time, with pressing then being released at the same time. Packets containing timing of pressing down and release of the connection buttons are then transmitted from each apparatus using multicasting. The times included in the packets are then compared with those recorded within the apparatuses, so as to enable both apparatuses to correctly identify each other. This connection method is scaleable as being able to detect duplicate connection requests. It is therefore possible to establish secure connection by exchanging public keys.