Neos\Flow\Http\Request::getClientIpAddress PHP Method

    public function getClientIpAddress()
    {
        $serverFields = array('HTTP_CLIENT_IP', 'HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR', 'HTTP_FORWARDED');
        foreach ($serverFields as $field) {
            if (empty($this->server[$field])) {
                continue;
            }
            $length = strpos($this->server[$field], ',');
            $ipAddress = trim($length === false ? $this->server[$field] : substr($this->server[$field], 0, $length));
            if (filter_var($ipAddress, FILTER_VALIDATE_IP, FILTER_FLAG_NO_RES_RANGE | FILTER_FLAG_NO_PRIV_RANGE) !== false) {
                return $ipAddress;
            }
        }
        return isset($this->server['REMOTE_ADDR']) ? $this->server['REMOTE_ADDR'] : null;
    }