Warning message in Bluetooth: TIOCGSERIAL is not supported - c++

Question

I want to link a Bluetooth barcode scanner (Gryphon GBT4400) in "client" mode to a Bluetooth-enabled PC with the serial port profile.
The Bluetooth PC adapter is Atheros Communications AR3012.
PC is running under Ubuntu Server 16.04.
I first run the following commands through bash script:
sdptool add --channel=22 SP > /dev/null
rfcomm watch /dev/rfcomm0 22 1>/dev/null 2>&1 &
Then with scanner I scan the barcode to link the scanner to the PC in Bluetooth (this barcode includes the MAC address of the Bluetooth interface of the PC).
It works well: PC and scanner are now connected.
Then I open the serial port through a QT/C++ application running on PC, built with QT 5.5.1, with following code:
pSerialPort = new QSerialPort("/dev/rfcomm0");
pSerialPort->open(QIODevice::ReadOnly);
At this step, this warning message is immediately displayed on PC:
Bluetooth: TIOCGSERIAL is not supported
Except this warning, everything works very well: the QT application retrieves correctly all the scanned barcode values.
I found almost nothing on the web.
Can someone help me to understand this warning message ?

Answer 1

You could remove all warning and error messages with:
qt_app 2>/dev/null
but that would hide other warnings that you might want to see. To hide just this one without having to change any source code and recompile, you can do:
qt_app 2>&1 | grep -v TIOCGSERIAL