socket.io - Failed to load resource: net::ERR_CONNECTION

I'm building a forum where two users after connections can post a status then comment on them. For comments, i used socket.io .

In console i'm getting this error each few seconds :

Failed to load resource: net::ERR_CONNECTION_REFUSED
GET http://localhost/socket.io/?EIO=4&transport=polling&t=O05nump net::ERR_CONNECTION_REFUSED

How to fix this error ?

I installed express, nodemon and socket.io in my socket server:

Socket server:

package.json

{
"name": "socket",
"version": "1.0.0",
"description": "",
"main": "app.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"keywords": [],
"author": "",
"license": "ISC",
"dependencies": {
  "express": "^4.17.3",
  "nodemon": "^2.0.15",
  "socket.io": "^4.4.1"
  }
}

app.js

const io = require("socket.io")(4000, {
cors: {
    origin: "http//localhost:3000",
},
});


io.on('connection', (socket) => {
  console.log('A new user is connected !');
})
io.on('disconnect', () => {
  console.log('User has left !');
});

Front:

Also, i installed socket.io-client in client (front), then in my web page, i added this code :

import { io } from 'socket.io-client'
export default () => {

  //implement socket
  const socket = useRef()

  useEffect(() => {
      socket.current = io("ws://localhost/4000")
  }, [])

return (
  //some html code
)
}

My project tree:

Project Forum

├── back     
├── client
   └──index.jsx
└── socket
   └──package.json
   └──app.js

Console Visual Studio Code: Visual studio code's console shows this only how much times i refresh browser or ctrl S the code:
```
[nodemon] starting 'node apde app.js'
```

CodePudding user response：

You added a slash instead of semi-colon:
socket.current = io("ws://localhost:4000")