Equisys technical notes

Technical guidance, explanations and fixes for our products

PRB: 'Error communication port fault' error when starting the Zetafax server



ID: ZTN1302

This Zetafax technical note applies to:

  • Zetafax 5.5 and later


Zetafax can be configured with fax modems that are class 1, 1.0, 2 and 2.0 compatible. Zetafax needs exclusive use of the com port and no other application or service can use it at the same time e.g. Internet connection dialling software.

These are the errors you might see when you start the Zetafax server and the com port is being used by another application.

            "Error opening com port "

            "Com port busy or in use"

You can also verify that the com port is in use by going into HyperTerminal and connecting directly to the com port. For more information on how to do this refer to section 5 in ZTN1000-PRB: Modem trouble shooting guide for Zetafax.

Note: Do not connect to the modem as Zetafax talks to the com port only. You will also get an error message saying com port is busy and in use.


To resolve this issue you will need to find out what application or service is using this com port. The most common ones are remote access service or Microsoft fax. If you are using other applications such as PC anywhere or other remote monitoring software then this would need to be disabled.

On rare occasion the com port might get in to a state where it detects there is a device or application attached but there isn't. To resolve this, a reboot of the machine is required.

Further information

For more information please refer to the following technical notes.

ZTN1000-PRB: Modem trouble shooting guide for Zetafax.

ZTN1003-INFO: Modem hang-up status codes for class 2.0 fax.

Last reviewed: 21 October 2005 (GC/XX)

Date Published: 25 July 2003 (GC/GW)

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