To read data that is coming from your COM port you need to know what the correct device is. Usually this is in /dev and is called something like /dev/ttyS0. To send data to the COM port simply redirect the output of an echo to the device:
echo “ping 192.168.1.1″ > /dev/ttyS0
This will send the command ping 192.168.1.1 to the COM port.
If you want to read from the COM port you need to concatenate the device:
cat /dev/ttyS0