Socket.io server over https - https

Question

I tried to convert the socket IO getting started example to https like this:
const fs = require('fs');
const app = require('https').createServer({
key: fs.readFileSync("privkey.pem"),
cert: fs.readFileSync("cert.pem"),
ca: fs.readFileSync("fullchain.pem"),
}, handler)
const io = require('socket.io')(app);
app.listen(443);
function handler (req, res) {
res.writeHead(200);
res.end();
}
io.on('connection', (socket) => {
socket.emit('news', { hello: 'world' });
socket.on('my other event', (data) => {
console.log(data);
});
});
But running the following in my browser does not work:
const ws = new WebSocket("wss://example.com");
But I received the following error:
Firefox can’t establish a connection to the server at wss://example.com/.
I tried to debug this by running this curl command:
curl -i -N -H "Connection: Upgrade" -H "Upgrade: websocket" -H "Host: example.com" -H "Origin: https://example.com " https://example.com
and the result was:
curl: (52) Empty reply from server
None of the console logging code is reached and there are no errors on the node script while doing all of this.
Why can't I connect to my websocket server?

Answer 1

According to doc:
Socket.IO is NOT a WebSocket implementation. Although Socket.IO indeed uses WebSocket as a transport when possible, it adds some metadata to each packet: the packet type, the namespace and the packet id when a message acknowledgement is needed. That is why a WebSocket client will not be able to successfully connect to a Socket.IO server, and a Socket.IO client will not be able to connect to a WebSocket server either.
So this is not correct:
const ws = new WebSocket("wss://example.com");
You should use:
const socket = io('https://your-server-address');