Delayed socket.io response, and "warn - websocket connection invalid" - node.js

Question

I am running a nodeJS + Express + socket.io + httpd application on an AWS EC2 instance.
Upon loading the page, the logger provides this information:
GET / 200 2ms - 1.23kb
GET /javascripts/script.js 304 1ms
debug - served static content /socket.io.js
GET /stylesheets/style.css 304 1ms
GET /stylesheets/style.css 304 1ms
GET /images/052.png 304 1ms
GET /Candara.ttf 304 1ms
debug - client authorized
info - handshake authorized EgWLPeyO2uiCTSui01CP
debug - setting request GET /socket.io/1/websocket/EgWLPeyO2uiCTSui01CP
debug - set heartbeat interval for client EgWLPeyO2uiCTSui01CP
warn - websocket connection invalid
info - transport end (undefined)
debug - set close timeout for client EgWLPeyO2uiCTSui01CP
debug - cleared close timeout for client EgWLPeyO2uiCTSui01CP
debug - cleared heartbeat interval for client EgWLPeyO2uiCTSui01CP
At this point, things will halt for about 5 seconds, after which:
debug - setting request GET /socket.io/1/xhr-polling/EgWLPeyO2uiCTSui01CP?t=1376937523124
debug - setting poll timeout
debug - client authorized for
debug - clearing poll timeout
debug - xhr-polling writing 1::
debug - set close timeout for client EgWLPeyO2uiCTSui01CP
debug - setting request GET /socket.io/1/xhr-polling/EgWLPeyO2uiCTSui01CP?t=1376937523490
debug - setting poll timeout
debug - discarding transport
debug - cleared close timeout for client EgWLPeyO2uiCTSui01CP
After this point, things start working well as far as I can tell, and events are fired and received without delays (if an event is fired before the 5 seconds delay described above, they will not be processed until after the delay has completed). The problem is how to remove that 5 seconds delay.
The client-side JS looks like this:
window.onload = function () {
var socket = io.connect("http://xxx.us-west-2.compute.amazonaws.com", {resource: "/socket.io"});
The server-side JS looks like this:
var express = require('express');
var app = express();
var io = require("socket.io").listen(app.listen(3000));
My httpd.conf file looks like this:
ProxyPreserveHost On
ProxyPass / http://localhost:3000/
ProxyPassReverse / http://localhost:3000/
<Proxy *>
Order deny,allow
Allow from all
</Proxy>
<Location />
allow from all
</Location>
How can I avoid the initial delay and establish a healthy connection to socket.io?

Answer 1

I fixed the problem by restricting the allowed transport methods to "xhr-polling" and "jsonp-polling". I believe this is because Apache/2.2.25 doesn't offer support for the others.
The relevant code was added server-side:
io.set("transports", ["xhr-polling", "jsonp-polling"]);