Originally Posted by AndyLandy
Can you be a little bit more-specific? If you do 'ls /dev/ttyS0', do you even have the relevant device entry?
Are you using a serial port on your PC, or are you using an add-on (PCI card or USB dongle)? Sometimes they are assigned different device names.
Thanks for replay
Yes i am using serial port on my pc ,when i am opening the file " fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);" And debugging it showing following message "opening_error: Permission denied" plz help