@Chong Hey I got it solved.
I changed the port to 4568 instead of 12001 and everything works well. It seems Ubuntu deals with these ports differently.
I am thinking of buying VPS from DigitalOcean (or may be Linode) as they both have VPS starting from $5 which is excellent.
My question is how easy is it to setup on VPS? Because I only know about PHP/MySQL/.Net and I have never done such installation before.
It's fairly simple as long as you have some experience with the Linux command line.
Installing NodeBB on a VPS with dependencies installed is very easy. You need to type a few commands in the terminal. The skills you would need is almost same as ability to copy paste commands from available tutorial. Try Ubuntu as OS. Good luck.