I could not make a connection to a FileZilla FTP server.
I installed the FTP Server and I could not connect from the internet facing side ?
I could connect on the server itself though, using the commandline FTP.exe
I checked to firewall where I had installed a NAT rule and all was fine
So it must be something with the local Windows Firewall.
Some years back I created a Windows log File Analyzer application using AutoIT. It’s dating from the XP timeframe but still working on Windows 2008r2
You need to activate the Firewall Logging, and can find the log file here.
So as you can see the packet was dropped by the local firewall.
Solution is to the create a custom Inbound Rule for the FileZilla program.
%ProgramFiles% (x86)\FileZilla Server\FileZilla Server.exe
Since we have a firewall in front of the server facing the public internet, we can define for Domain only.
Everthing is working fine now.