Section 6. A person not a resident of the commonwealth who engages in the business of providing direct broadcast satellite service to subscribers or customers in the commonwealth shall, as a condition precedent to engaging in such business and by so engaging in such business, be deemed thereby to appoint the state secretary as his agent for the service of process in any judicial proceeding under this chapter. Such process shall be served by delivering a copy of the process in the hands of the state secretary or a deputy or in the office of the state secretary. Such service shall be sufficient service upon the person; provided, however, that such notice of such service and a copy of the process shall, at least 15 days before the return day of such process, be sent by registered mail to such person's last known address, and that the sender's registered mail receipt and the commissioner's affidavit of compliance with this section shall be appended to the process and filed in the action or proceeding on or before the return day of the process or within such further time as the court may allow. The court in which the action or proceeding is pending may order such continuances as may be necessary to afford the defendant reasonable opportunity to defend the action. Service of process in the foregoing manner shall have the same force and validity as if served upon the taxpayer personally within the commonwealth.