我在 Heroku 上部署应用程序时遇到了 Socket io 问题

Question

I created a chat room using socket.io within my express app and it's working fine in local host when I deployed my application to heroku I get this error when I open the chat room

GET http://localhost:5000/socket.io/?EIO=3&transport=polling&t=N1PV-tt net::ERR_CONNECTION_REFUSED

here is my index.js file

var express = require("express")
var cors = require("cors")
var bodyParser = require("body-parser")
var app = express()
var mongoose = require("mongoose")
//var http = require('http').createServer(app);
var io = require('socket.io')(http)
var port = process.env.PORT || 5000
var server = app.listen(port);
var io = require('socket.io').listen(server);
var http = require('http');

let users = [];
let messages = [];
let index = 0;

app.use(bodyParser.json())
app.use(cors())
app.use(bodyParser.urlencoded({ extended: false }))

const mongoURI = 'mongodb+srv://1920:1920@cluster0-qyzs9.mongodb.net/liebherr?retryWrites=true&w=majority'

mongoose.connect(mongoURI, { useNewUrlParser: true })
    .then(() => console.log("MongoDB Connected"))
    .catch(err => console.log(err))

var Users = require("./routes/Users")

app.use("/users", Users)


//Socket connection

io.on('connection', (socket) => {
    io.emit('noOfConnections', Object.keys(io.sockets.connected).length)


    socket.on('disconnect', () => {
        console.log(`a user has left the chat.`);
        io.emit('noOfConnections', Object.keys(io.sockets.connected).length)
    })



    socket.on('chat-message', (msg) => {
        socket.broadcast.emit('chat-message', msg)
    })
    socket.on('typing', (data) => {
        socket.broadcast.emit('typing', data)
    })
    socket.on('stoptyping', () => {
        socket.broadcast.emit('stoptyping')
    })
})

    // Static folder
    app.use(express.static(__dirname + '/public/'));
    app.get(/.*/);

and here is package.json file

{
  "name": "express-demo",
  "version": "1.0.0",
  "description": "This is a full stack application",
  "engines": {
    "node": "13.1.0"
  },
  "main": "index.js",
  "scripts": {
    "start": "node index.js",
    "dev": "nodemon index.js"
  },
  "author": "Farouk Turki",
  "license": "ISC",
  "dependencies": {
    "bcrypt": "^3.0.7",
    "body-parser": "^1.19.0",
    "cors": "^2.8.5",
    "express": "^4.17.1",
    "jsonwebtoken": "^8.5.1",
    "mongodb": "^3.5.2",
    "mongoose": "^5.8.9",
    "nodemon": "^2.0.2",
    "socket.io": "^2.3.0"
  }
}

Everything is working fine except the chatroom so I need to know why it's still using port 5000 in localhost

Answer 1

From the front end (socket.io client) you are setting the hostname as localhost . But a front end code is not run server-side, it is in client side(your browser/or any thin client), it can access only the resources that are accessible over the internet(or the resources which is accessible by the browser itself).

So, in your case, the connection code will look something like:

<script>
  const socket = io('http://<your-heroku-public-url-for-the-express-server>');
  // which typically is 
  const socket = io('http://randomname.herokuapp.com');
</script>

Given that http://randomname.herokuapp.com is the public url of your node js server.