Serial Port....what's using it?

weazer used Ask the Experts™
I have a DEll 4600 running XP.  I'm using an external modem for DSL.

When I want to get photos from my digital camera onto the computer, it get's hooked up to the serial port.  The serial port is also used to program my X10 module.  Niether is done at the same time.

On my last computer, both worked on COM2.  On this machine when I try to use them, I get no connection and they indicate COM2 is in use by another program or piece of hardware.  I know the internal modem for voice and fax is using COM3.

How can I find what is using COM2.  I get no connection when trying to get the camera or X10 module on COM1.

Last....both of these devices worked when I first installed them and their software on the computer.
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Top Expert 2012

Get a readout on all your devices with Aida32:

You should be able to see if COM1 is working if you go into Control Panel->System->Hardware->Device Manager and look under Ports.
Endpoint Engineer
It may say its in use but what it really means is that there is a process locking the port (probably some background process) waiting for you to plug in an X10 device or the digital camera.  it constantly probes (or just listens passively) for the device to connect.  I've seen this many times with Palm handhelds/PDAs, and the easy fix is to just disable the application in question.

check device manager and remove any/all COM ports, I've seen some machines on XP with COM port problems and generally removing all the ports and letting XP re-detect them will fix it.  It could be a BIOS related problem also, Dell has had some BIOS-related serial port issues from time to time.  Or the COM1 might be set for IRDA mode in BIOS for some reason, press F2 at power-on to check that, it might be under "Legacy Peripherals" or "Integrated Peripherals" section.   I'll find you the latest update for that 4600.

Also, COM1 and COM3 typically (in the "old times" before ACPI) shared an IRQ, so you could try changing your modem properties to make it COM5 or 6, etc.



Followed your advice......solved the problem.
Kyle SchroederEndpoint Engineer

What specifically fixed it?  Removing and re-adding the ports?  Just curious to have a well-defined answer in case someone else finds this question in the future who is having the same/similar problem.



After doing all the various checks...I determined it was an application tieing up the port.  I finally did a system restore (which I was afraid to do being new to XP) from the day I knew everything including the camera and X10 module were able to communicate with COM 1.

Now everything works.

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