title: Socket.io trigger from server
body: <p>I'm asking myself : "How could I trigger an IO event to a specific user (like notification when sucess on something)". But on a post request for example I don't have any socket objet.</p>
  
  <p>I want to be able to do this: (should I store the socket object in a cookie? Or there are other possibilities availible?)</p>
  
  <pre class="lang-js prettyprint-override"><code>app.post('/askChangeUserPass', ChangePassIfCorrect , function (req, res){
      if (req.session) {
  
          if ( req.data == 1 ){
              return res.send("1") // socket.emit("notification", {})
          } else {
              return res.send("req.data") // socket.emit("notification", {})
          }
  
      } else {
          return res.render("404")
      }
  
  });
  </code></pre>