In linux redirect RS232 Serial Port traffic (in+out) to TCP port. Log all input + output to files. Its possible to connect with telnet to tcp-port. Short circuit COM pin 2+3 (in+out) to do loop-back test of connection without device attached, see http://www.ni.com/tutorial/3450/en/

linuxRedirectSerialPortToTcpWithLog.sh

#!/bin/bash

# netcat -l 7000 </dev/ttyUSB0 >/dev/ttyUSB0 &

cat /dev/ttyUSB0 | tee /var/log/lyngdorfSerial.ComToTcp.log | netcat -l 7000  | tee /var/log/lyngdorfSerial.TcpToCom.log > /dev/ttyUSB0 &

# Linux resets state when netcat closes com-port, so we need to se this after opening netcat
stty -F /dev/ttyUSB0 115200 cs8 -cstopb -parenb

killtree() {
    local _pid=$1
    local _sig=${2:--TERM}
    kill -stop ${_pid} # needed to stop quickly forking parent from producing children between child killing and parent killing
    for _child in $(ps -o pid --no-headers --ppid ${_pid}); do
        killtree ${_child} ${_sig}
    done
    kill ${_sig} ${_pid}
}

background_pid=$!	
trap "logger 'killing lyngdorf'; killtree $background_pid -KILL 2>/dev/null; exit" INT TERM EXIT

wait