Communication control server, communication terminal and communication control method

The invention provides a communication server, a communication terminal, and a communication control method thereof. Time required before PoC communication starts, in the case where a communication channel on the destination side has not been established, is shortened, and convenience of users is enhanced. A request for establishing a communication channel used for PoC communication is sent from a terminal TA. Immediately after receiving this request, call processing for establishing a communication channel to a terminal TC other than the terminal TA is started. In parallel with this call processing, processing after sending a response to the request is performed. Thereby, response to a communication channel connection request, SIP Registration processing and Invitation processing on the originating side and the processing on the destination side are performed in parallel, so that connection time can be shortened, and PoC communication can be started early.