title: Firebug displaying some Socket.IO requests in red others in black
body: <p>The same URL is displayed in red sometimes while in other times black.  I can't see a difference between the two requests.  Does anyone know why?</p>
  
  <p>The versions I use are:</p>
  
  <ul>
  <li>Firebug 2.0.17b1</li>
  <li>Firefox 43.0.1</li>
  <li>Socket.IO 1.4.5</li>
  <li>Node.js 6.3.0</li>
  </ul>
  
  <p>The server-side code is rather simple:</p>
  
  <pre><code>var http = require('http')
  var _server = http.createServer();
  var io = require('socket.io').listen(_server);
  
  // QUESTION: I still get CORS errors although I have these allowed origins:
  io.set('origins', "ws://localhost:* ws://127.0.0.1:* http://localhost:* http://127.0.0.1:*");
  
  _server.listen(63143);
  
  io.sockets.on('connection', function (socket) {
      console.log("EventServer: connection");
  
      socket.on('disconnect', function () {
          console.log("EventServer: disconnect");
      });
  });
  
  var url = require('url');
  _server.on('request', function (req, res) {
      console.log('EventServer: client request: ' + req.url);
  
      res.writeHead(200, {"Content-Type": "text/html"});
      //res.write('OK');  &lt;========= QUESTION: this throws 'write after end' exception. Why?
      res.end();
  });
  </code></pre>