By default node.js will listen only on localhost/127.0.0.1 for local requests. If you specify the IP address in your app as 0.0.0.0 it will listen on all IPs. Another option is to enter only the IP it will be used with (if using a floating IP this is the anchor IP, not the public floating IP users will use).

This shows an example that should listen publicly on port 6000 as long as there is not a firewall blocking it.

var http = require('http');

http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
}).listen(6000, "0.0.0.0");
console.log('Server running at http://0.0.0.0:6000/');

digital ocean blocking by default port above :6000 , dont know the reason but , if you will run node less then 6000 then only its working fine for web and APK else only working on APK…