Exception when execute modem_cliente in a loop

[waze96]

When the code execute the second call this exception appears:

INFO:root:Started /dev/ttyUSB0 #SECONDNUMBER 1 1 1
INFO:iec870ree.modem:try open port 0
INFO:iec870ree.modem:serial port /dev/ttyUSB0 opened
INFO:iec870ree.modem:read thread Starting
INFO:iec870ree.modem:sending command ATZ
Exception in thread Thread-1:
Traceback (most recent call last):
File "/usr/lib/python3.8/threading.py", line 932, in _bootstrap_inner
self.run()
File "/usr/lib/python3.8/threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
File "/usr/local/lib/python3.8/dist-packages/iec870ree-0.6.0-py3.8.egg/iec870ree/modem.py", line 144, in read_port
File "/usr/local/lib/python3.8/dist-packages/pyserial-3.4-py3.8.egg/serial/serialposix.py", line 494, in read
buf = os.read(self.fd, size - len(read))
TypeError: an integer is required (got type NoneType)
INFO:iec870ree.modem:R-ATZ

INFO:iec870ree.modem:R-OK

INFO:iec870ree.modem:sending command AT+CBST=7,0,1
INFO:iec870ree.modem:R-AT+CBST=7,0,1

INFO:iec870ree.modem:R-OK

The error comes from the 494 line of serialposix.py, here: buf = os.read(self.fd, size - len(read))
Problem is that self.fd is None after the first number, any idea of how fix this?

[ecarreras]

It seems like is a problem in the connection with the modem, can you try upgrading pyserial package? or you can use the modem directly with the terminal?