How to make a Server for Websocket secure with node.js

My websocket server, based on node.js, works for ws:// but not for wss://

The server runs on my Raspberry Pi B 3+. Now that I have changed ws:// to wss:// in my JavaScript file, it does not work anymore.

The node.js server:

const WebSocket = require('ws');
var wss = new WebSoket.Server({ port: 4445 });

wss.on('connection', function connection(ws) {
    console.log("New client connected.");

    ws.on('message', function incoming(data) {
        console.log(data);
        ws.close();
    });

    ws.on('close', function close() {
        console.log("Client disconnected.");
    });

});

The JavaScript client:

var connection = new Websocket('wss://myDomain:4445');

connection.onopen = function () {
    connection.send("Hello");
    connection.close();
}

connection.onerror = function (error) {
    console.log(error);
    connection.lose();
}

'myDomain' is a subdomain that refers to the IP of the Raspberry Pi via dns. I get the following error:

WebSocket connection to 'wss://myDomain:4445/' failed: Error in connection establishment: net::ERR_CONNECTION_CLOSED

Copyright Notice：Content Author:「Paul」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/56923070/how-to-make-a-server-for-websocket-secure-with-node-js