If you’re logging to FTP account by using any of FTP client and the server hangs on welcome message and then disconnected automatically here is the quick solution for this problem:
Login to your server via SSH with root details
Find the resolver file usually located in /etc/resolv.conf
Edit it using any file editor i will use nano in this example:
Now, the file is opened in text editor just replace or rewrite the IPs for nameservers listed in this file:
Save the file by CTRL + O and then exit from editor by CTRL + X
You’re done, now FTP should work with out any issue.
These above IPs are of OpenDNS resolver IPs that are free to use.