§ 11-c. Copy of notice of lien to a contractor or subcontractor with respect to public improvements liens. Within five days before or simultaneously with filing a notice of lien in accordance with section twelve of this chapter or the filing of an amendment of a notice of lien in accordance with section twelve-a of this chapter with respect to a public improvement lien, the lienor shall serve a copy of such notice or amendment by certified mail on the contractor, subcontractor, assignee or legal representative for whom he was employed or to whom he furnished materials or if the lienor is a contractor or subcontractor to the person, firm or corporation with whom the contract was made. A lienor having a direct contractual relationship with a subcontractor or a sub-subcontractor but not with a contractor shall also serve a copy of such notice or amendment by certified mail to the contractor. The notice of lien so filed shall contain thereon or there shall be filed therewith proof of service of a copy of said lien upon the parties required to be served pursuant to this section, and failure to file proof of such service shall render the notice of lien a nullity. Any lienor, or a person acting on behalf of a lienor, who fails to serve a copy of the notice of lien as required by this section shall be liable for reasonable attorney's fees, costs and expenses, as determined by the court, incurred in obtaining such copy.