websocket polling fallback

client-fallback

ioSocket = io.connect("http://www.mydomain:443/chatserver");

ioSocket.of('/chatserver').on('connect', function()
{
   // Everything works fine
   console.info("Connected to Chat-server");
}).on('connect_failed', function(reason)
{
   /* Connection failed. This can have many reasons.
      One possible reason is the blocking of port 443 which I used above.
      In this case, the given reason-argument is just "undefined".
      So if you want to have a more specific handler, you could do the following steps
      only if reason == undefined. (not tested though)
   */
   io.transports = ['xhr-polling']; // Limit transport to xhr-polling now. This is possible on client-side, too!
   ioSocket = io.connect("http://www.mydomain:443/chatserver");
   console.info("Using XHR-polling because of connection issue: "+reason);
   ioSocket.of('/chatserver').on('connect', function()
   {
      // Now, everything works. Fallback successful!
      console.info("Connected to Chat-server");
   }).on('connect_failed', function(reason)
   {
      // Still not working..
      console.error ("Connection failed: "+reason);
   });
});