Err Msg: 425 Can't Open Data Connection (236001)


The information in this article applies to:

  • Microsoft Proxy Server 2.0
  • Microsoft Windows NT Server 4.0
This article was previously published under Q236001

SYMPTOMS

When you use an IIS 4.0 FTP server and Microsoft Proxy Server installed on Microsoft Windows NT Server 4.0 with the Server Proxy feature, the following error may be displayed on FTP clients:
425 Can't open data connection

CAUSE

This error occurs when two or more users, using a non-passive mode FTP client, are simultaneously accessing the same IIS 4.0 FTP server located behind the Proxy Server.

RESOLUTION

A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

The English version of this fix should have the following file attributes or later: 
   Date      Time                 Size    File name     Platform
   -------------------------------------------------------------
   06/16/99  07:53p               173,328 Wspsrv.exe    Alpha
   06/16/99  07:54p               262,416 Wspwsp.dll    Alpha
   06/16/99  07:54p                96,528 Wspsrv.exe    x86
   06/16/99  07:55p               141,072 Wspwsp.dll    x86

STATUS

Microsoft has confirmed that this is a problem in Proxy Server 2.0.

MORE INFORMATION

This fix is for Windows NT Server 4.0 running IIS

After you apply the fix mentioned here, you need to modify the Wspcfg.ini file located in the Winnt\System32\Inetsrv folder to allow FTP port 20 to be bound to the external interface of Proxy Server. This is due to a FTP functionality change in IIS 4.0 that forces the port to listen remotely and locally instead of just locally as in previous IIS versions.

The Wspcfg.ini file should look like the following example:

[Inetinfo]
ServerBindTcpPorts=21,20
LocalBindTcpPorts=20
Persistent=1
KillOldSession=1
ForceCredentials=1

After you make this change, stop the internal IIS computer where FTP is located by using the following steps:
  1. At a command prompt, type net stop iisadmin /y.
  2. Type net start msftpsvc.
  3. If Web publishing, type net start w3svc.
  4. Test for FTP functionality from the Internet.
NOTE: Wspsrv.exe should be installed on the Microsoft Proxy Server 2.0 computer and Wspwsp.dll should be installed on the Microsoft Proxy 2.0 Client.

NOTE: Install the Wspwsp.dll file on the client computer. For a Windows computer the Wspwsp.dll file should go into the Windows folder and for a Windows NT or Windows 2000 computer it should go into the System32 folder.
Modification Type:MinorLast Reviewed:9/22/2005
Keywords:kbHotfixServer kbQFE kbbug kbfix kbQFE KB236001
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