public function verifyConnection(array $connectionHeader) {
        foreach ($connectionHeader as $l) {
            $upgrades = array_filter(
                array_map('trim', array_map('strtolower', explode(',', $l))),
                function ($x) {
                    return 'upgrade' === $x;
                }
            );
            if (count($upgrades) > 0) {
                return true;
            }
        }
        return false;
    }