There is no response from my VPS when I connect to the ftp service on port 21. It's a Linux server with kloxo and pure-ftp. I have been using it without troubles from past 8 months. I installed ConfigServer before few months, which didn't create any troubles but to check, I have disabled it.
It starts working at sometime for few minutes and then again stops for like 2-3hours and then again work for like 10-20minutes.
I tried connecting using telnet and it was blank response but after a few minutes, it started working.