protected function getDefaultRequestHeaders($host, $key, $origin)
    {
        return [
            self::HEADER_HOST => $host,
            self::HEADER_UPGRADE => self::UPGRADE_VALUE,
            self::HEADER_CONNECTION => self::CONNECTION_VALUE,
            self::HEADER_KEY => $key,
            self::HEADER_ORIGIN => $origin,
            self::HEADER_VERSION => $this->getVersion(),
        ];
    }