Socket.io + node JS = Error during handshake: error code 500 - node.js

Question

I was working on Socket.io and node jS to develop a chat web app. It worked locally but I have faced many issues when I deployed my changes to Azure app service.
I am creating a secure connection on port 443. I have resolved other issues but I can't resolve this one.
This the error I'm getting in console on client side.
WebSocket connection to 'wss://mydomain/socket.io/?EIO=3&transport=websocket' failed: Error during WebSocket handshake: Unexpected response code: 500
This is how I'm connecting on server side
var socket = io.connect("https://mydomain:443", {transports: ['websocket'], secure: true, port: '443'});
and this is my server.js code:
const express = require("express");
const mongoose = require("mongoose");
const bodyParser = require("body-parser");
const passport = require("passport");
const users = require("./routes/api/users");
const base = require("./routes/api/base");
const leads = require("./routes/api/leads");
const requests = require("./routes/api/requests");
const offApp = require("./routes/api/offApp");
const chat = require("./routes/api/chat");
const chatSocket = require("./routes/socket/chat");
const path = require("path"); // on top
const app = express();
const cors = require('cors')
const https = require('https');
const fs = require('fs');
var options = {
pfx: fs.readFileSync('certificate.pfx'),
passphrase: 'password'
};
app.use(cors());
var server = https.createServer(options, app);
var client = require("socket.io").listen(server);
client.origins('*:*');
client.set('transports', ['websocket']);
server.listen(443);
// Bodyparser middleware
app.use(
bodyParser.urlencoded({
extended: false
})
);
app.use(bodyParser.json());
// DB Config
const db = require("./config/keys").mongoURI;
// Connect to MongoDB
mongoose
.connect(
db,
{ useNewUrlParser: true }, (err, db) => {
if (err) {
throw err;
}
console.log('MongoDB connected');
chatSocket(db, client);
});
// Passport middleware
app.use(passport.initialize());
// Passport config
require("./config/passport")(passport);
// Routes
app.use("/api/users", users);
app.use("/api/base", base);
app.use("/api/leads", leads);
app.use("/api/requests", requests);
app.use("/api/offapp", offApp);
app.use("/api/chat", chat);
const port = process.env.PORT || 5000;
app.use(express.static("client/build")); // change this if your dir structure is different
app.get("*", (req, res) => {
res.sendFile(path.resolve(__dirname, "client", "build", "index.html"));
});
app.listen(port, () => console.log(`Server up and running on port ${port} !`));
I have checked the logs, there are no errors there.