While the Arduino family of boards connect to your computer using a USB virtual serial port, the ATmega ones have an actual serial connection on-board.

Serial Port Monitor from Eltima The Serial Port Monitor software tool from Eltima Software is, in fact, a professional port sniffer and analyzer system utility good for RS232/RS422/RS485 port ...

While Octave will never have the rich instrument control options available to MATLAB users, there are still ways to get serial data directly from a connected device into Octave. The Octave: ...

Eight digital outputs act as the parallel interface. When a byte is received over serial, the individual bits are set on the individual digital lines connected to the printer’s parallel port.