Port 3000 already in use. Nodejs, Socket,IO

Question

No other process runs on port 3000 except this

Here's the part of a program

const port = process.env.port || 3000;

app.listen((port), () => console.log(`listening to port ${port}`));

const io = require("socket.io")(port) //Here's the problem.

Problem appears when I add port 3000

If I manually write some other port like 4000. It works

Shall I create another port for socket.io?

In case of port 3000

The error looks like this

listening to port 3000
events.js:292
      throw er; // Unhandled 'error' event
      ^

Error: listen EADDRINUSE: address already in use :::3000

Emitted 'error' event on Server instance at:
    at emitErrorNT (net.js:1345:8)
    at processTicksAndRejections (internal/process/task_queues.js:80:21) {
  code: 'EADDRINUSE',
  errno: -4091,
  syscall: 'listen',
  address: '::',
  port: 3000
}
[nodemon] app crashed - waiting for file changes before starting...

Does this answer your question? [Node / Express: EADDRINUSE, Address already in use - Kill server](https://stackoverflow.com/questions/4075287/node-express-eaddrinuse-address-already-in-use-kill-server) — Lawrence Cherone, Jul 19 '21 at 20:16
@LawrenceCherone it doesn't. I think we can't run socket.io and express server on same port — Sarah, Jul 19 '21 at 20:24
socket.io and express can share the same server so can run on the same port — Lawrence Cherone, Jul 19 '21 at 20:32
lmgtfy: https://stackoverflow.com/questions/12235406/how-to-use-expressjs-and-socket-io-on-a-same-port — Lawrence Cherone, Jul 19 '21 at 20:33
@LawrenceCherone I think it's unresolved for now. nothing is working. — Sarah, Jul 19 '21 at 20:43

score 0 · Answer 1 · edited Jul 19 '21 at 20:34

0

In the terminal try this to find the active port:

Windows

netstat -ano | findstr :3000

Mac/Linux

lsof -iTCP:3000 -sTCP:LISTEN

Then kill using the PID:

kill <PID>

or this if the above doesn't work

kill -9 <PID>

edited Jul 19 '21 at 20:34

Zoe

27,060
21
118
148

answered Jul 19 '21 at 19:47

Mikey Lau

11
3

isof is unrecognized to the terminal. i use windows – Sarah Jul 19 '21 at 19:54
Try ```netstat -ano | findstr :3000``` instead. – Mikey Lau Jul 19 '21 at 20:17
3000 is only running on this project. – Sarah Jul 19 '21 at 20:23

score 0 · Answer 2 · answered Jul 19 '21 at 19:48

0

It means that there is a process that uses 3000 port, try to kill that process and start the application again.

answered Jul 19 '21 at 19:48

Levon Baghoyan

170
4

this is a project and it all runs on 3000 – Sarah Jul 19 '21 at 19:55
Your project may still be running in the background by the time when you want to start it again. – Levon Baghoyan Jul 21 '21 at 11:05

Port 3000 already in use. Nodejs, Socket,IO

2 Answers2