A communication device performs P2P communication with the other communication device by establishing a session through a server, and includes a first transmitting portion, if the communication device operates as a called device requested to establish the session, upon the receiving a session start message from the other communication device, transmits to the other communication device a response message including information on a port for directly receiving data from the other communication device; a session establishing portion establishes the session by transmitting a control message to a port specified by information in the session start message or a response message received from the other communication device; a command accepting portion accepts a user's command permitting to receive from the other communication device; and a starting portion starts transmitting and receiving of data to and from the other communication device, upon the accepting of the command.