The reference numeral 4 designates a relay server, 41 a communication unit, 42 a control unit, 5 a local system, 51 a terminal, 52 a gateway, and 53 a LAN. The local system 5 is a system similar to the local system 1 and the local system 2, and is formed by the terminal 51, the gateway 52 and the like being connected by the LAN 53.