private function ftp()
    {
        $servers = static::SERVERS;  // Server list
        // Try each server till success
        $ftp;
        for ($i = 0; $i < count($servers); $i++) {
            $ftpServer = $servers[$i]['domain'];
            $ftp       = ftp_connect($ftpServer);

            // Return resource on connected
            if ($ftp) {
                if (ftp_login($ftp, 'anonymous', null)) {
                    if (ftp_chdir($ftp, $servers[$i]['path'])) {
                        if (ftp_pasv($ftp, true)) {
                            return $ftp;
                        }
                    }
                }
            }
        }

        // Unable to connect to a server
        throw new \Exception('Unable to connect to server to download data');
    }