MacOS – FTP not working on any FTP client not even with Mozilla or Chrome

I am using a MacBook Pro with OS X 10.10.3. I am a developer and I use FTP on a regular basis. However I am new to OS X. It was working fine but suddenly FTP stops working for all FTP clients on my Mac for any server, even for ftp://ftp.mozilla.org/. I use NetBeans and use its most native Java based client. I tried with Firebug, FileZilla, Firefox, Chrome and OS X's native Finder client. I tried with Terminal as well — the response is:

Tousifs-MBP:~ tousifosman$ ftp -v ftp://ftp.mozilla.org/
Trying 63.245.215.56...
Connected to ftp.mozilla.org.
421 Service not available, remote server has closed connection.
ftp: Can't connect or login to host `ftp.mozilla.org'

However I am able to connect to all the servers from my Windows platform.