RS232

with an USB/serial adapter (/dev/ttyUSB0)

cu:

 cu -s 115200 -l /dev/ttyUSB0

ttylog:

 ttylog -d /dev/ttyUSB0 -b 115200

or minicom:

 minicom -D /dev/ttyUSB0 -b 115200

if the device is not found, you can try:

 sudo chown user /dev/ttyUSB0