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On a Windows Server 2003 R2-based computer, you are running the FTP utility of Subsystem for Unix-based Applications (SUA). When an FTP client receives the SIGWINCH signal while it reads the control session socket from the FTP server, the FTP session is terminated. Additionally, you receive the following error message:
421 Service not available, remote server has closed connection.
Note The SIGWINCH signal may be generated when the C shell command prompt window appears.
This problem occurs because the FTP command does not mask the SIGWINCH signal when it reads the FTP control session socket.
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.
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:
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.
To apply this hotfix, the computer must run Windows Server 2003 R2. Also, SUA must be installed.
You do not have to restart the computer after you apply this hotfix.
Hotfix replacement information
This hotfix does not replace a previously released hotfix.
To use this hotfix, you do not have to make any changes to the registry.
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.
Windows Server 2003 R2, x86-based version
Windows Server 2003 R2, x64-based version
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
More information about the SIGWINCH signal, visit the following Web site: