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 .