Reopening serial port fails if not closed properly with CloseHandle

c++ windows serial-port createfile
superg picture superg · Jun 1, 2010 · Viewed 9.7k times · Source

I am working with USB device on Windows that is seen as a virtual serial port. I can communicate with the device using CreateFile and ReadFile functions, but in some cases my application does not call CloseHandle (when my application in development crashes). After that all calls to CreateFile fail (ERROR_ACCESS_DENIED), and the only solution is to log in to my computer again. Is there any way to force closing the open handle (or reopening) programmatically?

Answer

Hans Passant picture Hans Passant · Jun 1, 2010

This is certainly not normal. Windows automatically closes any handles that are left open after the process terminates. This must be a flaw in your USB device driver, although it is hard to see how it could mess this up. The ones that emulate serial ports are however notoriously lousy. Well, nothing much you can do but hope for a driver update from the manufacturer. Or a device from another manufacturer.

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