PyQt5 QSerialPort QSocketNotifier: Invalid socket specified

I had a code on PyQt4 and I was working with pyserial, like this:

Code:

---

import serial
global ser
 
def setting_COMPort():
    global ser
    ser = serial.Serial(
              port='/dev/ttyAMA0',
              baudrate = 115200,
              parity=serial.PARITY_NONE,
              stopbits=serial.STOPBITS_ONE,
              bytesize=serial.EIGHTBITS,
              timeout=1)

---

and when I wanted to send something to serial port I did just:

Code:

---

ser.write(":010600000044b5\r\n")

---

Easy, simple and worked stable and perfect. But I needed some function which were unavaliable in serial, so I changed to PyQt5 and QSerialPort. Now my code have this Gestalt:

Code:

---

from PyQt5.QtSerialPort import QSerialPort
from PyQt5 import QtCore
 
def setting_COMPort(ser): # ser is an object of QSerialPort
    ser.setBaudRate(QSerialPort.Baud115200)
    ser.setParity(QSerialPort.NoParity)
    ser.setOpenMode(QSerialPort.ReadWrite)
    ser.setStopBits(QSerialPort.OneStop)
    ser.setDataBits(QSerialPort.Data8)

---

but sending data to serial seems not to be so easy on this way. So now with the power of PyQt5 I am doing it like this in function:

Code:

---

# ser is the same object of QSerialPort
s=":010600000044b5\r\n"
data_to_send=QtCore.QByteAray(s)
ser.write(data_to_send)

---

But I am getting the error QSocketNotifier: Invalid socket specified

There are some tries to find a solution on the web, but nothing real.

So what am I doing incorrect, why this way to send a string through QSerialPort does not work?