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I am trying to troubleshoot a problem on a Windows 2003 server. An application needs to make use of a serial port but it appears some other application has the port open.

How can I identify what other application has the port open?

I have tried using SysInternals PORTMON but it is unable to attach to the serial port (COM1) reporting back that Portmon could not attach to SerialO-the device may be in use.

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You can use Process Explorer (from Sysinternals, too) to see which process has an open handle to the port.

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