If you are trying to connect to your FTP account and keep losing your connection or you notice that the server firewall is blocking your IP when connecting with FTP after a few moments, see below for helpful advice in resolving this pesky issue.
What we’ve described above is typical when your server is not set up to accept passive connections properly.
First, log in to your server and edit the following file:
#PassivePortRange 30000 50000
Remove the comment from the beginning of this line. I like to change the range to 30000 35000 but you can leave it as it. Just make sure the correct corresponding ports are open in the firewall as well.
Exit and restart FTP via command line or the restart tool in WHM.
Once that’s done, log in to WHM and find ConfigServer Firewall (CSF) under Plugins.
Click on the button that says “Firewall Configuration.”
Scroll down a little bit until you see TCP_IN and TCP_OUT
Add the open passive ports to both areas as follows:
Scroll all the way down and click on Change.
That’s it! Connecting with FTP will work flawlessly now.