title: Socket.io EADDRNOTAVAIL error
body: <p>I oppened port of 120 on my firewall and i open ufw port on my server (Ubuntu 16.04)
  But when run this code ;</p>
  
  <pre><code> var app = require('express')();
  var http = require( "http" ).createServer( app );
   var io = require( "socket.io" )( http );
   http.listen(120, "xxxx.xxx.xx");
  
  
   io.on('connection',function(socket){
   console.log("A user is connected");
   });
  </code></pre>
  
  <p>I get this error ;</p>
  
  <pre><code> throw er; // Unhandled 'error' event
        ^
  
  Error: listen EADDRNOTAVAIL xxxx.xxxxxx:120
      at Object.exports._errnoException (util.js:870:11)
      at exports._exceptionWithHostPort (util.js:893:20)
      at Server._listen2 (net.js:1224:19)
      at listen (net.js:1273:10)
      at net.js:1382:9
      at nextTickCallbackWith3Args (node.js:452:9)
      at process._tickCallback (node.js:358:17)
      at Function.Module.runMain (module.js:444:11)
      at startup (node.js:136:18)
      at node.js:966:3
  </code></pre>