In an effort to transmit/receive MDI data in a session among a plurality of terminals, when any of the terminals designates a communication partner and transmits a request to join a session to a management server 100, the management server allows the terminal to join a session joined by the designated communication partner, allocates a channel different from those allocated to the other terminals in the session, and notifies the allocated channel together with information on the terminals joining the session. Further, the terminal sets communication destinations based on the notification.