The double flush() is not the root cause; the real issue is that code is trying to use the serial port after it has been closed.
The error occurs both in close() (during flush()) and later in _writeBytes() (during write()), indicating the port is closed or invalid at those times.
This ensures flush() is only called if the stream is open, and logs (but ignores) any exceptions during flush. This should prevent the "Bad file descriptor" error.
I see this error a lot on a rak unit, I dont know this is the way but .. you be the judge.
Some devices (e.g. Heltec V3.1) are reset when the RTS or DTR pins are
messed with, which means that without workarounds, Meshtastic CLI will
cause a reset with any operation that opens the serial port.
This behavior is documented in this PySerial issue:
https://github.com/pyserial/pyserial/issues/124
On Linux, we already handle this by disabling the HUPCL termios flag,
which has the effect of preventing the offending lines being toggled. On
Windows, setting the initial state of RTS and DTR before opening the
port has a similar effect.
Implement this workaround so that Meshtastic CLI can be used on Windows
with these devices.
