SERVER DEVICE THAT SETS SECURITY LEVELS IN ACCORDANCE WITH DISTANCES BETWEEN DEVICES, CLIENT DEVICE, COMMUNICATION SYSTEM, INTEGRATED CIRCUIT FOR SERVER CONTROL, INTEGRATED CIRCUIT FOR CLIENT CONTROL, SERVER PROGRAM, CLIENT PROGRAM, METHOD FOR CONNEC

摘要

Disclosed are a server device, client device, and the like that can change security strengths in accordance with distances between devices without requiring high-performance terminal implementations. The disclosed server device (100), which provides a service to client devices (200), is provided with an information management unit (110), an optical signal transmission unit (120), and a service provision unit (130). A plurality of types of connection information that are needed when connecting to the service and have different importance levels are associated with importance levels, stored, and managed by the information management unit (110). The optical signal transmission unit (120) modulates the stored plurality of types of connection information into an optical signal wherein the higher the importance level a piece of connection information is associated with, the less the effect on the light intensity. Said optical signal is then transmitted via first communication functionality. When a connection request accompanying a prescribed type of connection information is made by a client device (200) via second communication functionality, the service provision unit (130) uses the connection information to provide the service to the client device (200).