> Ruben J=F6nsson ha scritto:
> > For example: The PC software is talking to a virtual serial port that is
> > connected to a USB device. When the PC software has opened the port it =
never
> > expects the port to go away, which is reasonable considering that a sta=
ndard
> > serial port can't be unplugged. However, when the USB device is unplugg=
ed
> > (perhaps by accident) really weird things can happen with the PC softwa=
re. I
> > have not been able to reliably catch any exceptions caused by this and =
most of
> > the time the PC software just hangs. Sometimes I even have had to resta=
rt the
> > computer (XP) before I can get the communication up and running again.
> =

> =

> In theory, a WM_DEVICECHANGE message (in Windows) should alert you of =

> what is going on. I say in theory since I'm more or less aware of the =

> subtle details in that :)

I think I have tried that too but when the WM_DEVICECHANGE is raised it is =

already too late. And when you have to deal with these things anyway I thin=
k it =

is best to skip the virtual serial port and speak straight to the USB devic=
e =

instead.

> =

> I used mostly HID Generic devices: in them, the Handles usually become =

> no longer valid, both Reads and Writes usually Fails, and so do =

> semaphores and Waits... so you can more or less recover.
> =


Yes, that is my point. Talk to the device via the USB classes since they ca=
n =

handle a disconnected device. Avoid the virtual serial port since the drive=
rs =

for these can't (at least not what I have seen so far).

Merry Christmas /Ruben
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
Ruben J=F6nsson
AB Liros Electronic
Box 9124, 200 39 Malm=F6, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
ruben@pp.sbbs.se
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D

-- =

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