Conn. Gen. Stat. § 52-59c

In any action brought to foreclose a mortgage or judgment, tax or mechanic's lien, the attorney of record for any nonresident attaching creditor, nonresident judgment lienor or nonresident mortgagee who has commenced a foreclosure action on such mortgage shall be the agent for service of process upon the creditor in the foreclosure and further service shall not be required. Service of process shall be made by the officer to whom the process is directed upon the attorney by leaving with or at the office of the attorney, at least twelve days before the return day of the process, a true and attested copy thereof, and by sending to the defendant at his last-known address, by registered or certified mail, postage prepaid, a like true and attested copy, with an endorsement thereon of the service upon the attorney.