COMMUNICATION RELAY DEVICE, COMMUNICATION TERMINAL DEVICE, COMMUNICATION METHOD, COMMUNICATION PROGRAM, AND RECORDING MEDIUM

摘要

A communication system (100) includes a communication terminal device (120) for performing communication within a group formed by a plurality of predetermined communication terminal device (120) (hereinafter, referred to as an in-group communication); and a communication relay device (110) for relaying the in-group communication. A reception unit (111) of the communication relay device (110) receives start request information requesting start of the in-group communication from a communication terminal device (120) belonging to the group. According to the start request information received by the reception unit (111), a transmission unit (112) transmits participation request information requesting for participation in the in-group communication to the other communication terminal device (120) belonging to the group.