Deploying nodejs app with Open Shift PaaS

I'm starting with Open Shift PaaS and I picked a node.js app as my first try.

So far I'm getting a 503 when I try to access my app site.

I've tried:

Set my github repo,
set the ssh key at github and made Open Shift have it,
created a very simple app using express (I did install express by npm)
did commit and pushed all changes,
I did install rhc and ran rhc app restart -a nodejs

But I can't get it to work.

The rhc tail -a nodejs outputs:

DEBUG: Error: Cannot find module '/var/lib/openshift/531be41fe0b8cd3d12000003/app-root/runtime/repo/server.js'
    at Function._resolveFilename (module.js:337:11)
    at Function._load (module.js:279:25)
    at Array.0 (module.js:484:10)
    at EventEmitter._tickCallback (node.js:190:38)

DEBUG: Program node server.js exited with code 1

DEBUG: Starting child process with 'node server.js'

This is my app.js file:

var express = require('express')
var server = new express()
server.use(express.static(__dirname+"/public"))


server.get('/', function (request, response) {
    response.send(200)
})

server.listen(process.env.OPENSHIFT_NODEJS_PORT || 80)

EDIT

I've renamed app.js to server.js, did git add, commit and push, restarted app with rhc. but it's not working yet though.

You can name your main script whatever you want, as long as the contents of your package.json file accurately describes your recommended server init process

I've written up a blog post that outlines the two main steps for getting your Node.js project to run on OpenShift:

Update your package.json file, documenting your server init process (main, scripts.start).
Adapt your code to rely on environment variables for runtime configuration details: server ip, port, domain name, db passwords, and other custom tokens

Make sure to document your preferred deployment process in your project's README file as well