For easiest operation we do not specify the individual device address of the serial port, but a generic one named /dev/logger. On the system, where this program is supposed to operate, we then set a symbolic link to the appropriate device and give it the appropriate permissions. We have to do this as root:
# cd /dev # rm -f logger # ln -s ttyS0 logger # chmod a+rw logger
/dev/ttyS0 is the first serial port on old Linux systems. It seems that the /dev/cua* devices are obsoleted on newer versions and that one should now use /dev/ttyS0 and subsequent ports. Subsequent serial ports have higher numbers (ttyS1, ttyS2, ...).
For more details consult Michael R. Sweet (1999) Serial Programming Guide for POSIX Operating Systems. 5th edition. http://www.easysw.com/mike/serial/index.html.