title: Runs on localhost:4000 but not on ec2-ip:4000
body: <p>I have a nodejs app running on port 4000. I have developed it in my Vagrant box running Ubuntu 16.04 where I am able to curl both <a href="http://localhost:4000" rel="nofollow noreferrer">http://localhost:4000</a> and <a href="http://vagrant-IP:4000" rel="nofollow noreferrer">http://vagrant-IP:4000</a>. </p>
  
  <p>However, when I replicate the same set-up on an EC2 instance, I am able to curl only on <a href="http://localhost:4000" rel="nofollow noreferrer">http://localhost:4000</a> and not on <a href="http://ec2-public-IP:4000" rel="nofollow noreferrer">http://ec2-public-IP:4000</a>. </p>
  
  <p>In both cases server is listening on 0.0.0.0 and CORS is enabled. (Here, vagrant-IP and ec2-public-IP are actual IPv4 addresses). How can I fix this?</p>