FTP over TLS connection to remote server works from FileZilla but doesn't work from WinSCP

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ravens
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FTP over TLS connection to remote server works from FileZilla but doesn't work from WinSCP

I need to connect to a client's FTP server. The connection should be FTPS (explicit FTP over TLS) with port 21. This works from FileZilla, but it doesn't work with WinSCP.
I have attached the log files for both.
Can anyone please help me resolve this?
  • winscp.log (5.83 KB, Private file)
  • filezilla.log (3.05 KB, Private file)

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martin
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Re: FTP over TLS connection to remote server works from FileZilla but doesn't work from WinSCP

Your FTP server is misconfigured to return an invalid IP address 0.0.0.0 in PASV command response.
Both WinSCP and FileZilla, when encountering an invalid address they ignore it and open the data connection to the original address of the server. But WinSCP does not identify 0.0.0.0 as an invalid address, so it won't employ the workaround.
Though note that this is only a workaround, the fault is still on the server's side.
You can make WinSCP to ignore the address unconditionally using session option Force IP address for passive mode connections:
https://winscp.net/eng/docs/ui_login_ftp

I'll improve WinSCP to recognize IP addresses starting with a zero as invalid:
Issue 2224 – Recognize IP addresses starting with zero in FTP PASV response as unroutable

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ravens

Thank you so much!
I will report this to the client if they may want to re-configure it on their end. But using the setting to force IP did work both on WinSCP GUI and .NET app where I use this. That resolves issue on my end.

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