Substituted service permits affixing a duplicate summons at a person's residence when personal service cannot be effected. If service cannot be effected despite due diligence under the prescribed modes, the serving officer shall affix a duplicate summons to a conspicuous part of the house where the person ordinarily resides; thereafter the court, after making such inquiries as it thinks fit, may declare the summons duly served or order fresh service in such manner as it considers proper.