502 Bad Gateway nginx google app engine - node.js

Question

I am building a NodeJS application using express here is my code:
var express = require('express');
var app = express();
var session = require('express-session');
var uuidv1 = require('uuid/v1');
require('dotenv').config();
var APIAI_TOKEN = process.env.APIAI_TOKEN;
var APIAI_SESSION_ID = uuidv1();
app.use(express.static(__dirname + '/views')); // html
app.use(express.static(__dirname + '/public')); // js, css, images
var server = require('http').createServer(app);
var port = process.env.port || 3000;
server.listen(port, function() {
console.log('Server listening at port: ', port);
// console.log(APIAI_SESSION_ID);
// console.log(APIAI_TOKEN);
});
app.use(session({
genid: function(req) {
return APIAI_SESSION_ID;
},
secret: 'secret',
saveUninitialized: true,
resave: true
}));
var io = require('socket.io')(server);
var apiai = require('apiai')(APIAI_TOKEN);
var rp = require('request-promise');
//#region Web UI
app.get('/', function(req, res) {
res.sendFile('index.html');
});
I start my app with node app and everything works perfectly on my localhost but when I deploy the app to Google App engine i get a 502 bad gateway error and when i check the log it happens at the app.get() method.
I even deployed it to Heroku server as well, the app is crashing at the same point. What could be wrong with my code?
Here is the log form Heroku server:
2017-11-01T16:35:57.528020+00:00 heroku[router]: at=error code=H10
desc="App crashed" method=GET path="/" host=ippcbot.herokuapp.com request_id=d956df30-8352-4a54-80e6-2aa1fc96276b fwd="197.210.37.211" dyno= connect= service= status=503 bytes= protocol=https
2017-11-01T16:35:58.138751+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=ippcbot.herokuapp.com request_id=96b2bf0d-df05-4d7e-9018-0b09e1dfa748 fwd="197.210.37.211" dyno= connect= service= status=503 bytes= protocol=https
Disconnected from log stream. There may be events happening that you do not see here! Attempting to reconnect...
2017-11-01T16:19:36.517868+00:00 app[web.1]: npm ERR! Please include the following file with any support request:
2017-11-01T16:19:36.513572+00:00 app[web.1]: npm ERR! There is likely additional logging output above.
2017-11-01T16:19:36.517927+00:00 app[web.1]: npm ERR! /app/npm-debug.log
2017-11-01T16:19:36.584087+00:00 heroku[web.1]: Process exited with status 1
2017-11-01T16:19:36.607609+00:00 heroku[web.1]: State changed from starting to crashed
2017-11-01T16:20:47.248202+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=ippcbot.herokuapp.com request_id=41e9f39b-e908-4cee-a430-0d7f44a17590 fwd="197.210.37.211" dyno= connect= service= status=503 bytes= protocol=https
2017-11-01T16:20:47.891459+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=ippcbot.herokuapp.com request_id=9f244daf-7a3e-405e-b445-2fadd8b2735b fwd="197.210.37.211" dyno= connect= service= status=503 bytes= protocol=https
2017-11-01T16:35:13.187594+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=ippcbot.herokuapp.com request_id=455ccd5e-e389-49be-b892-e5e222c9864f fwd="197.210.37.211" dyno= connect= service= status=503 bytes= protocol=https
2017-11-01T16:35:13.805998+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=ippcbot.herokuapp.com request_id=112a5f08-632e-463d-b8e8-ed6de13b3596 fwd="197.210.37.211" dyno= connect= service= status=503 bytes= protocol=https
2017-11-01T16:35:57.528020+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=ippcbot.herokuapp.com request_id=d956df30-8352-4a54-80e6-2aa1fc96276b fwd="197.210.37.211" dyno= connect= service= status=503 bytes= protocol=https
2017-11-01T16:35:58.138751+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=ippcbot.herokuapp.com request_id=96b2bf0d-df05-4d7e-9018-0b09e1dfa748 fwd="197.210.37.211" dyno= connect= service= status=503 bytes= protocol=https

Answer 1

Not sure about Heroku, but for App Engine does changing the port to 8080 work?
For example:
const server = app.listen(8080, () => {
const host = server.address().address;
const port = server.address().port;
console.log(`Example app listening at http://${host}:${port}`);
});
From Run Express.js on Google App Engine Flexible Environment