Nodejs + Socket.io + https?

Question

Node.js

Created certificates via let's encrypt.
Got the files. Connected via nginx privkey.key fullchain.pem.
The domain has successfully started working on https and writes that it is protected.

But connecting the same certificates to the application. The client, when accepting them, rejects them with an error.
net::ERR_CONNECTION_CLOSED

Server-side code.

var fs = require('fs');

var options = {
  key: fs.readFileSync('ssl/privkey.pem'),
  cert: fs.readFileSync('ssl/fullchain.pem')
};

var httpServer = require('http').createServer();
var httpsServer = require('https').createServer(options);
var ioServer = require('socket.io');

var io = new ioServer();
io.attach(httpServer);
io.attach(httpsServer);
httpServer.listen(7165);
httpsServer.listen(7166);

io.sockets.on('connection', function (socket){});

From the client side

var port = location.protocol === 'https:' ? 7166 : 7165;
var socketIO = io(0.0.0.0:'+port);

socketIO.once('connect', function(){});

Answer 1

But connecting the same certificates to the application. The client, when accepting them, rejects them with an error.

Because the certificates are issued for a specific domain. This domain should be specified in

var socketIO = io('0.0.0.0:'+port);