Communication system and communicating method

A communication system for communicating with a plurality of communication terminals by using an ad-hoc network comprising:

• a first communication terminal;
• a second communication terminal;
• and
• a third communication terminal, wherein
• the first communication terminal transmits message data addressed to the third communication terminal to a plurality of communication terminals,
• the second communication terminal receives the message data, confirms a destination of the received message data, and transfers the received message data to other communication devices when the confirmed destination is not the second communication terminal itself,
• the third communication terminal receives the message data, confirms the destination of the received message data, and transmits response data corresponding to the received message data to the first communication terminal that is a transmission source of the received message data when the confirmed destination is the third communication terminal itself,
• a priority for transmission of the response data is set higher than that of the transferred message data, and
• a period of time from reception of the message data until the transmission of the corresponding response data is shorter than a period of time from reception of the message data until transfer of the message data.