Counterpart terminal management system, communication terminal, communication system, counterpart terminal management method, and recording medium storing counterpart terminal management program

A communication system, comprising:

• a counterpart terminal management system;
• and
• a communication terminal that is participating in a session with at least a counterpart communication terminal, the communication terminal including terminal circuitry that
• receives information indicating that the counterpart communication terminal is not registered as a candidate counterpart terminal for the communication terminal, from the counterpart terminal management system, when the communication terminal leaves from a session transmitting content data among the plurality of communication terminals, the information indicating terminal identification information for identifying the counterpart communication terminal that participates in the session,
• controls displaying of a user interface component that allows a user to send a request for adding the counterpart communication terminal as a candidate counterpart terminal for the communication terminal, and
• transmits the request for adding the counterpart communication terminal as a candidate counterpart terminal for the communication terminal, to the counterpart terminal management system, in response to selection of the user interface component by the user, wherein
• the counterpart terminal management system is configured to communicate with the communication terminal, and includes
• a memory that stores, for each one of a plurality of communication terminals configured to request to start communication with one or more candidate counterpart terminals, terminal identification information for identifying the communication terminal in association with counterpart terminal identification information for identifying the one or more candidate counterpart terminals, and
• system circuitry that transmits, to the communication terminal, the information indicating that the counterpart communication terminal is not registered as a candidate counterpart terminal for the communication terminal, based on whether counterpart terminal identification information of the counterpart communication terminal is stored in the memory for the communication terminal.

A method of managing information regarding one or more counterpart communication terminals, the method comprising:

• storing in a memory, for each one of a plurality of communication terminals configured to request to start communication with one or more candidate counterpart terminals, terminal identification information for identifying the communication terminal in association with counterpart terminal identification information for identifying the one or more candidate counterpart terminals;
• transmitting, to a first communication terminal that has left from a session transmitting content data among the plurality of communication terminals, information indicating terminal identification information for identifying a second communication terminal that participates in the session;
• receiving a request for adding the second communication terminal as a candidate counterpart terminal for the first communication terminal from the first communication terminal, the request for adding being generated based on information indicating that the second communication terminal is not registered as a candidate counterpart terminal for the first communication terminal;
• and
• storing the terminal identification information of the second communication terminal in association with the terminal identification information of the first communication terminal in response to the request for adding.