Error message when you use an FTP client in Windows XP: "500 Invalid PORT Command"

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Article ID: 911162 - View products that this article applies to.
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SYMPTOMS

When you use an FTP client on a computer that is running Microsoft Windows XP, you may receive the following error message:
500 Invalid PORT Command
This problem occurs when Windows Firewall is enabled on the network connection.

CAUSE

This problem occurs because the Application Layer Gateway Service for Windows XP does not recognize TCP ports that are lower than 1025 as valid FTP ports. When the FTP client uses a port that is lower than 1025, the FTP host receives an invalid port command. Therefore, the FTP connection cannot be established.

RESOLUTION

Hotfix information

A 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. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

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, contact 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=support
Note 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.

Prerequisites

No prerequisites are required.

Restart requirement

You must restart your computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The 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.
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File nameFile versionFile sizeDateTime
Alg.exe5.1.2600.281144,54414-Dec-200501:08

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

MORE INFORMATION

When this problem occurs, Network Monitor may show that the port command that the FTP client uses is 0,0,0,0,0,0.

For more information about the Application Layer Gateway Service, visit the following Microsoft Web site:
http://msdn2.microsoft.com/en-us/library/ms998420.aspx
For more information about the terms that are used in this article, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

Properties

Article ID: 911162 - Last Review: October 9, 2011 - Revision: 3.0
APPLIES TO
  • Microsoft Windows XP Professional
  • Microsoft Windows XP Home Edition
Keywords: 
kbautohotfix kbftp kbfix kbHotfixServer kbqfe KB911162

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