Windows 7 64-bit Serial Port problem


  • Applications can't access the serial port, get "Serial port in use" or such. PuTTY, Hyperterm, TeraTerm, various others.

    The serial port is Com1, in device manager the OS detects the correct modem (USR V.92) and will retrieve info from the modem, so the hardware works. I've also used 'echo atdt 12345 > com1' successfully form the command line. Again, the hardware works.

    But not other application can access the port. Portmon from sysinternals ( running in compatibility also can't see the port., it gets and "error 2".

    This port is connected to my modem (used for remote access to the craft/management/console port of various devices) which is scripted for testing all the far-end modems -- the script of course will fail if it can't control the modem. This port is also used locally for testing/configuring other equipment via a craft/management/console port.

    The problem is not drivers (se above about the hardware working) but rather that there appears to be some Win7 process that is holding the com port.

    Wednesday, May 04, 2011 9:47 PM


  • Hi,


    What device and application has this issue?


    Portmon is not compatible for Windows 7. Not each application will work under compatibility mode. Make sure your other applications are compatible with Windows 7 64-bit.


    Best Regards,


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    Friday, May 06, 2011 8:28 AM