This invention provides, for each apparatus, one communication control unit that generically controls communication between a relay server and a communication client or a communication server in each apparatus. More specifically, each communication control unit creates a communication socket that designates a predetermined port and an IP address indicating a local apparatus, and exchanges data between the communication server and the communication client via the communication socket, adjusting and relaying communication data between HTTP and the communication protocol of each of the communication server and the communication client.