Wordpress xmlprc not working in https

Recently, I have updated my site using an SSL and all URIs are now "https://".

My site is developed with Symfony 2 and mixing a Wordpress installation inside Symfony 2 web/wordpress directory.

All regular access is fine. Only one question:

In my Symfony 2, there is this code snippet:

private function getRecentPosts($num = 4)
{
    require_once 'wordpress/wp-includes/class-IXR.php';

    $user      = '11111';
    $pwd       = '22222';

    $host='https://www.rsywx.net';
    $script='/wordpress/xmlrpc.php';
    $port=443;

    $client = new \IXR_Client($host, $script, $port);

    $params = array(0, $user, $pwd, $num);
    $client->query('metaWeblog.getRecentPosts', $params);

    $wp = $client->getResponse();

    return $wp;
}

When my site is not wrapped with https, the above code works fine. But now it is under https, the above code is not working. If I dump the $client variable after the query function call, it gives an error like:

+error: IXR_Error {#256 ▼
    +code: -32300
    +message: "transport error - could not open socket"

Any hints? Do I need to tweak my WP?