title: What does binding a Rails Server to 0.0.0.0 buy you?
body: <p>I am using "www.xip.io" as a DNS wildcard for testing on different devices. I set my primary domain to my IP address. I fire up a rails server with <code>bundle exec rails server</code> and I go here <code>www.&lt;ip_address&gt;.xip.io:3000</code> and notice my rails server doesn't respond.</p>
  
  <p>However, if I bind my rails server to 0.0.0.0 like so <code>bundle exec rails server -b 0.0.0.0</code>, it works! I don't understand what 0.0.0.0 is telling my server for this to work. Can someone make sense of this?</p>