Node server port error

So I was working in Node, Express and connecting to MongoDB.
I am using Nodemon to watch for changes.
All was well until I installed create-react-app.
My file structure is

| - backend
|      | - server.js
| - frontend //react app lives here
|      | - src
|      ...

When I cd into the backend folder and start the server I get this error:

      throw er; // Unhandled 'error' event

Error: listen EACCES: permission denied 4000;
    at Server.setupListenHandle [as _listen2] (node:net:1415:21)
    at listenInCluster (node:net:1480:12)
    at Server.listen (node:net:1579:5)
    at Function.listen (C:\Users\Owner\Desktop\Learning JS\Backend\teachers-pet\backend\node_modules\express\lib\application.js:635:24)
    at C:\Users\Owner\Desktop\Learning JS\Backend\teachers-pet\backend\server.js:13:13
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
Emitted 'error' event on Server instance at:
    at emitErrorNT (node:net:1459:8)
    at processTicksAndRejections (node:internal/process/task_queues:83:21) {
  code: 'EACCES',
  errno: -4092,
  syscall: 'listen',
  address: '4000;',
  port: -1
[nodemon] app crashed - waiting for file changes before starting...

My server.js file:

const dotenv = require('dotenv');
const express = require('express');
const mongoose = require('mongoose');

const app = express();


const PORT = process.env.PORT || 8000;

        app.listen(PORT, () => {
            console.log('connected to db & listening on port 4000');
    .catch(err => console.log(err));

If I type out app.listen(4000 , () => {...}) server runs. But when I include the PORT variable or write out process.env.PORT it crashes.
When I console log process.env.PORT it logs the correct port number.

Even when I use the || operator it should switch to the specified port, but it still wouldn’t !
Why is this happening? Am I missing something that I should be aware of?


1 Like

I’ve just pushed all recent changes.
Repo: GitHub - ibrahimaq/post-a-gram: A social media app

I fixed it! I feel stupid and a fool. Embarrassment level 99. You’ll laugh at this.
I went off screen, rested my eyes and came back to spot a typo.
Even though I doubled, tripled and gazillion checked everything, including .env file I failed to spot a semi-colon in my .env PORT variable:


I think the light reflection off the screen had a play in it :face_with_spiral_eyes:.

But regardless, why didn’t the OR operator || get executed in the line:

const = process.env.PORT || 4000

Right… yes ofcourse, if it turns into a string, which is truthy, then ofcourse the the second expression after the || will not get executed.

Thank you for explaining it.

Honestly, we have all made a mistake like this at some point!

i face same error but i don’t understand it how to solve it

This was also my mistake. Thank you!