How to set secure websocket connection using websocket-server and node.js

I can't set secure websocket connection using websocket-server and node.js

server side

var options = {
    key: fs.readFileSync(PRIVATE_KEY),
    cert: fs.readFileSync(CERTIFICATE)
};

// create web server
var server = ws.createServer(options);
server.listen(8000);
...

client side

<script language="javascript" type="text/javascript">
    var wsUri = "wss://url:8000";


    function init() {            
        websocket = new WebSocket(wsUri);
    }

    ...

    window.addEventListener("load", init, false);
</script>

But it works for ws

var wsUri = "ws://url:8000";

Any ideas?

Copyright Notice：Content Author:「Mikhail.Mamaev」，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/7209243/how-to-set-secure-websocket-connection-using-websocket-server-and-node-js