FIX: "Unable to connect to FTP server" error in BizTalk Server 2010 if the FTP adapter uses SSL to connect to an FTP server

Symptoms

Consider the following scenario:

  • You use the FTP adapter in Microsoft BizTalk Server 2010 to connect to a third-party FTP server. The FTP server uses the Secure Sockets Layer (SSL) feature.

    Note The FTP server complies with Request for Comments (RFC) 4217.

  • The FTP adapter tries to transmit or receive messages from the FTP Server.

In this scenario, messages are not transmitted or received. Additionally, the following error message is logged in the Application log:

Error details: Unable to connect to FTP server "<FTP Server name>" as user "<user name>". Inner Exception details: "An error occured while reading a response from the server. This could be due to the timeout settings. Also check whether the FTP server has SSL enabled and uses implict SSL as the FTPS connection mode. "

Note In this error message, the word "occured" is a misspelling of the word "occurred," and the word "implict" is a misspelling of the word "implicit."

Cause

This issue occurs because of an error in the Xceedftpbiztalk.dll module.

When the FTP adapter uses the Xceedftpbiztalk.dll module, some SSL and TLS libraries send an empty (0-byte) data buffer as its first encrypted data buffer. However, the FTP adapter cannot decrypt an empty (0-byte) data buffer.  

Resolution

Cumulative update information

The hotfix that resolves this issue is included in cumulative update package 2 for BizTalk Server 2010.

For more information about how to obtain the cumulative update package, click the following article number to view the article in the Microsoft Knowledge Base:

2573000 Cumulative update package 2 for BizTalk Server 2010

Status

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

References

For more information about how to configure an FTP send port, visit the following MSDN website:

How to configure an FTP send port
For more information about how to configure an FTP receive location, visit the following MSDN website:

How to configure an FTP receive locationFor more information about Request for Comments (RFC) 4217, visit the following Internet Engineering Task Force (IETF) website:

General information about RFC 4217For more information about BizTalk Server hotfixes, click the following article number to view the article in the Microsoft Knowledge Base:

2003907 Information about BizTalk Server hotfixes

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