When you try to execute the git push command and the deployment status is SUCCESS. However the open shift return an error 503 – Service Temporarily Unavailable

artheman@localmachine /home/mywebappblog (master) $ git push origin master
Counting objects: 4, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (4/4), 341 bytes | 0 bytes/s, done.
Total 4 (delta 2), reused 0 (delta 0)
remote: CLIENT_MESSAGE: Stopping Node.js application...
remote: CLIENT_RESULT: Node.js application stopped.
remote: Building git ref 'master', commit 63efa24
remote: CLIENT_RESULT: Node.js modules installed.
remote: Preparing build for deployment
remote: Deployment id is 291b0274
remote: Activating deployment
remote: CLIENT_MESSAGE: Starting Node.js application...
remote: CLIENT_RESULT: Node.js application started.
remote: -------------------------
remote: Git Post-Receive Result: success
remote: Activation status: success
remote: Deployment completed with status: success
To ssh://123456789@mywebappblog.rhcloud.com/~/git/mywebappblog.git/
   7783eb5..63efa24  master -> master

When accessing the website https://mywebappblog-myaccount.rhcloud.com I got this error Service Temporarily Unavailable
The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

In Express.JS, to fix it make sure that your app properly listen to the correct Port number and IP address. Use process.env.OPENSHIFT_NODEJS_PORT and process.env.OPENSHIFT_NODEJS_IP

 * Get port from environment and store in Express.
var port = process.env.NODE_PORT || process.env.OPENSHIFT_NODEJS_PORT || 4010;
port = normalizePort(port);
var ip = process.env.NODE_IP || process.env.OPENSHIFT_NODEJS_IP || '';
app.set('port', port);

var server = http.createServer(app);
server.listen(port, ip); 
server.on('error', onError);
server.on('listening', onListening);

Note: If using the old node.js version use process.env.NODE_IP & process.env.NODE_PORT otherwise use the process.env.OPENSHIFT_NODEJS_PORT & process.env.OPENSHIFT_NODEJS_IP variables.
That’s it.. it should be working now.