help about write data RS232

[datbui]

Check baud rate, stop bits and parity settings. Defaults for serial library are 115200, 1 stop bit, no parity.

Thank you for your replay!
I checked, I use : Baud rate 115200, 1 stop bit, no parity.
I wrote string 'gh', Result: '  L'.
Thanks you.
My code in Resident:

if not port then
  require('serial')
  port = serial.open('/dev/RS232', { baudrate =115200 })
  port:flush()
  line = ''
end
port:write('gh')