A multi-port apparatus used to communicably connect a computer and a plurality of apparatuses connected to the computer through the computer serial communication ports, such as two computer serial communication ports. A second serial communication port of the computer is connectable to ports corresponding to the plurality of apparatuses desired to be communicated with. A changeover switch is controlled through a first serial communication port of the computer to select one of the plurality of the apparatuses to connect with the second serial communication port of the computer and communicating with the one apparatus through the second serial communication port.