Patent ID: 7864715

Claim:
A data communication method of a half-duplex mode where transmission and reception cannot be simultaneously performed when a first communication terminal and a plurality of second communication terminals communicate with each other via a communication server system, comprising transmitting data from a first communication terminal to a plurality of second communication terminals via the communication server system; invalidating the input of a send key of an input unit of the first communication terminal after the first communication terminal starts transmitting the data; transmitting a first notification for notifying the completion of reception from each of the plurality of second communication terminals to the communication server system when each of the plurality of second communication terminals finishes receiving the data from the first communication terminal and invalidating the input of a send key of an input unit of each of the plurality of second communication terminals when each of the second communication terminals finishes receiving the data; transmitting a second notification for notifying that all of the plurality of second communication terminals finished receiving the data from the communication server system to the first communication terminal and each of the plurality of second communication terminals when the communication server system receives the first notification from all of the plurality of second communication terminals; and permitting the input of the send key to all of the plurality of second communication terminals when all of the plurality of second communication terminals receive the second notification from the communication server system.