Socket IO net::ERR_CONNECTION_REFUSED on AWS EC2 using ELB - node.js

Question

I'm running a React app with node/express on an AWS EC2 instance using an Elastic Load Balancer.
Socket io runs fine when I access the EC2 instance directly but as soon as I access the app using the ELB url (http or https) it returns with GET current url net::ERR_CONNECTION_REFUSED pinged every second or so.
I have used AWS Certificate Manager to create a public certificate for the load balancer in order to be able to access the app via https. Here are the listeners I have enabled for ELB:
Listeners on ELB
On the client side I have the socket set up like so (used with react context):
let socket
const getMsg = (dispatch) => {
if(!socket){
socket = io(':3000', {secure: true})
socket.on('chat msg', function(msg){
dispatch({type:'RECEIVE_MSG', payload: msg})
})
}
}
const sendChat = (dispatch) => {
return async (value) => {
socket.emit('chat msg', value)
getMsg()
}
Here's part of the back-end code:
const app = express()
const http = require('http').createServer(app)
const io = require('socket.io')(http);
app.use(cors())
app.use(bodyParser.json())
app.use(methodOverride('_method'))
io.on('connection', socket =>{
console.log("new connection...")
socket.on('chat msg', async (msg) => {
io.emit('chat msg', msg)
});
})
const mongoUri = //hidden
mongoose.connect(mongoUri, {
useNewUrlParser: true,
useCreateIndex: true,
useUnifiedTopology: true
})
mongoose.connection.on('connected', () => {
console.log('you are connected')
})
mongoose.connection.on('error', (err) => {
console.log('connection error, please check your network settings')
})
http.listen(3000, ()=>{
console.log('Listening on 3000')
})
Do I need to setup my backend to accept https requests? Everything else within the app works fine using http on the node/express side even though I'm accessing the app using an https url. The only issue I'm having with requests to the express server is just with socket.io.

Answer 1

I'll add a note here, because I think this is valuable info: I ran into a similar issue a while back, you cannot use HTTP(s) listeners when trying to support web sockets on Classic ELBs.
Instead you can setup TCP SSL termination, and send the TCP to your backend which would allow regular http and ws traffic to work.
(Described here: https://www.built.io/blog/websockets-on-aws-s-elb#:~:text=AWS%20ELB%20doesn't%20support,IP%20information%20is%20not%20obtained)
Otherwise, you could opt for an ALB which does support the listeners as configured. I think ALB is likely the best option here, as it's sort of the "supported" solution from a infrastructure POV.