nodejs / express / socket.io site that Facebook crawler can't find

nodejs / express / socket.io site that Facebook crawler can't find

My site ideas.modernassemb.ly isn't getting found by the Facebook crawler,
it just comes back saying "URL returned a bad HTTP response code."
I'm somewhat new to NodeJS, but this is how I've set up my main file to
serve the index file:
var app = express.createServer();
var io = require('socket.io').listen(app, {log: false});
var publicDir = __dirname.replace(/\/server\/bin$/, '') + '/public_html';
app.use(express.bodyParser());
app.use('/', express.static(publicDir));
app.listen(process.env.PORT || 8080);
I know I'm missing something, not sure how to send back a response code
that will make the Facebook crawler happy?
And my og:meta tags are all there on the index.html page:
<meta property="og:image"
content="http://modernassemb.ly/assets/img/src/facebooklogo.png"/>
<meta property="og:title" content="Open Source Ideas"/>
<meta property="og:description" content="We believe our ideas should roam
free, whether they are silly, practical, functional, or conceptual. They
will live here, with the hopes that you'll see something you'd like to
collaborate with us on."/>
<meta property="og:url" content="https://ideas.modernassemb.ly"/>
<meta property="og:site_name" content="Open Source Ideas"/>