Express only works on port 3000 - node.js

Question

My app only works on port 3000.
If i change port to anything else, it'll work but when a page loads it occurs this error.
abc is not defined
at eval (eval at compile (C:\Users\ASUS\node_modules\ejs\lib\ejs.js:549:12), :22:26)
at returnedFn (C:\Users\ASUS\node_modules\ejs\lib\ejs.js:580:17)
at tryHandleCache (C:\Users\ASUS\node_modules\ejs\lib\ejs.js:223:34)
at View.exports.renderFile [as engine] (C:\Users\ASUS\node_modules\ejs\lib\ejs.js:437:10)
at View.render (C:\Users\ASUS\node_modules\express\lib\view.js:128:8)
at tryRender (C:\Users\ASUS\node_modules\express\lib\application.js:640:10)
at EventEmitter.render (C:\Users\ASUS\node_modules\express\lib\application.js:592:3)
at ServerResponse.render (C:\Users\ASUS\node_modules\express\lib\response.js:971:7)
at C:\Users\ASUS\Desktop\nodeweb\controllers\index.js:21:6
at Layer.handle [as handle_request] (C:\Users\ASUS\node_modules\express\lib\router\layer.js:95:5)
abc is a variable i'm using in index.ejs, defined in router.
var express = require('express');
var router = express.Router();
router.get('/', function(req, res) {
res.render('index', {abc: 23})
});
module.exports = router;
I'm starting my server with node app command
var app = express();
app.set('view engine', 'ejs')
app.use(express.static(__dirname + '/public'));
app.use(require('./controllers'))
app.listen(8080, function() {
console.log('Listening on port 8080...')
})
UPDATE
I think i found the problem
It works when i use
app.use('/', function(req, res) {
res.render('index', {tit:[1,2,3,4,5]});
})
instead of
app.use(require('./controllers'))
But why?
UPDATE
It just fixed itself, it works normally now and i don't know why. That sucks.

Answer 1

You could try hard coding the port:
app.set("port", process.env.PORT || 3000);
Or this:
$ PORT=8080 node app.js
Also if you are not on Windows, and want to use ports bellow 1024 try this first:
sudo PORT=80 node app.js

Answer 2

If you want to place the route handlers in a separate file, then you can, just no need to call the file with app.use(...).
Instead, you can just do:
require('./controllers');
It has nothing to do with the abc variable.

Answer 3

It is because , I think controller is not properly imported . If you write like this I think, it will work fine
var router = require('express').Router();
router.get('/', function(req, res) {
res.render('index', {abc: 23})
});
module.exports = router;
var app = express();
var route = require('./router')
app.set('view engine', 'ejs')
app.use(express.static(__dirname + '/public'));
app.use('/',route);
app.listen(8080, function() {
console.log('Listening on port 8080...')
})
Here be careful when you define require('./router') in var route = require('./router') ,because it is relative so it totally depends on your folder structure.