[Prob]Sending AT commands through COM PORT

[Debasish Mandal]

I am trying to send SMS using sending AT commands to a GPRS mobile device in windows enviornment.I can send sms when i am sending commands using Hyper Terminal.but the problem is when i am Sending those commands using the following scripts its becoming unsuccessful.
Here is my code:

import time
import serial
# configure the serial connections
ser = serial.Serial(
	port='COM8',
	baudrate=115200,
	parity=serial.PARITY_NONE,
	stopbits=serial.STOPBITS_ONE,
	bytesize=serial.SEVENBITS
)
at_r = 'AT\r'
sms_r = 'AT+CMGF=1'
dest_r = 'AT+CMGS="+9190074xxx43"'
call_r = 'ATDT +919339xxxx05\r'   #I can dial successfully 
msg_r = 'This is text Message!!!!'
msga_r = 'This is text Message!!!!\n'
ser.isOpen()

#ser.write('AT+CGMM\r')             #working fine i can read the device name.
ser.write(at_r)                    
#ser.write(call_r)                  #Dial No. working fine
ser.write(sms_r)                    #Set the mode to SMS mode
ser.write(dest_r)                   #Set Destination
ser.write(msga_r)                   #Set Text
ser.write(chr(26))                  #write ctrl+z inthe port

#give device time to answer
time.sleep(1)
line = ''
line = ser.read(19)
print line
ser.close()