How to deploy socket io & express server on heroku - node.js

Question

I'm trying to deploy socket io + express server on heroku for a chat application but i am facing a trouble while deploying the server .
First this is my server code
var express = require('express');
var app = express();
var server = require('http').createServer(app);
var io = require('socket.io').listen(server);
users = [];
connections = [];
server.listen(process.env.PORT || 3000);
console.log('Server running...');
io.sockets.on('connection',function(socket){
connections.push(socket);
console.log('Connected %s sockets connected ', connections.length);
//Disconnect
socket.on('disconnect', function(data){
users.splice(users.indexOf(socket.username),1);
connections.splice(connections.indexOf(socket),1);
console.log('Disconneted : %s sockets connected',connections.length);
});
});
This is my package.json file
{
"name": "",
"version": "1.0.0",
"description": "chat application",
"main": "index.js",
"scripts": {
"start": "node index"
},
"author": "",
"license": "ISC",
"dependencies": {
"socket.io": "*",
"express": "*"
}
}
But I'm getting this error
Cannot GET /

Answer 1

Had the same problem (socket.io with express and react).
You can add to server this line:
app.use(express.static('some path to a static file'));
e.g.
app.use(express.static('client/build'))
works for me assuming in package.json has this line at "scripts":
"heroku-postbuild": "NPM_CONFIG_PRODUCTION=false npm install --prefix client && npm run build --prefix client"

Answer 2

This error has nothing wrong deployed application. Your app still waits for connection on port 3000 (or port from process.env.PORT). App responds "Cannot GET /" because you don't have any routes.
To see how routes can be implemented look at this -> https://expressjs.com/en/starter/hello-world.html
To see how connect using socket.io (client part) look at this -> https://socket.io/get-started/chat/#Integrating-Socket-IO