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Error message when you try to run an application that you developed by using the "return quickly" feature of the Windows COM port driver: "Error reading comm device"
Article ID: 957264 - View products that this article applies to.
You develop an application by using the "return quickly" feature of the Windows COM port driver. For example, you develop an application that uses the serial port control (MsComm32.ocx) that is included with Microsoft Visual Basic 6.0 to redirect a COM serial port. However, when you run the application on a Windows XP-based terminal server, the application may be unable to access the redirected COM serial port on the local computer. Additionally, you receive an error message that resembles the following:
Run-time error '8020':
Error reading comm device
This problem occurs because the MSComm32.ocx control uses the "return quickly" feature of the Windows COM port driver. The redirected port implementation sets the status to pending. This setting affects the functionality of the MSComm32.ocx control.
Hotfix informationA supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.
If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.
Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:
http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.
PrerequisitesTo apply this hotfix, you must have Windows XP Service Pack 2 or a later service pack installed on the computer. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/322389/ )How to obtain the latest Windows XP service pack
Restart requirementYou must restart the computer after you apply this hotfix.
Hotfix replacement informationThis hotfix does not replace any other hotfixes.
File informationThe English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
Windows XP with Service Pack 2, x86-based versions
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Windows XP with Service Pack 3, x86-based versions
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Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
841700For more information, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/841700/ )BUG: You receive an "error reading comm device" error message when you try to read from a COM port that is on a remote computer by using the MSComm control in Visual Basic 6.0
(http://support.microsoft.com/kb/838291/ )Some applications cannot access the serial port in Windows Server 2003