A communication system including a plurality of terminals; and a switchboard connected to the terminals, includes a means for causing each of the terminals to register an identifier and an address of the terminal itself in the switchboard; a means for, when one of the terminals transmits a request of transmitting a list of the terminals connected to the switchboard, causing the switchboard to transmit the list of the terminals to the terminal that transmits the request; a means for, when the terminal that transmits the request selects one of the terminals from the list and transmits the identifier of the selected terminal to the switchboard, causing the switchboard to transmit the address of the selected terminal to the terminal that transmits the request; and a means for causing the terminal that transmits the request to establish a communication with the selected terminal using the received address and a default port number.