hi , i use huawei e303. but in my /dev folder i dont have any file named ttyUSB% but they are tty% and ttyS%. when i command dmesg | grep tty i see tty0 enabled. and when i try your code this error release : File "fsms.py", line 110, in SMSC_number = get_SMSC_from_dongle() #get_SMSC_number File "fsms.py", line 61, in get_SMSC_from_dongle output = dongle.readline() File "/usr/local/lib/python2.7/dist-packages/pyserial-2.7-py2.7.egg/serial/serialposix.py", line 475, in read raise SerialException('device reports readiness to read but returned no data (device disconnected or multiple access on port?)') serial.serialutil.SerialException: device reports readiness to read but returned no data (device disconnected or multiple access on port?) can any one help me ? thank a lot.