Rodalies de Catalunya is the train network that will take you from Barcelona to Malgrat de Mar. Get on the R1 line towards Maçanet-Massanes or Blanes. The journey Barcelona-Malgrat de Mar lasts approximately 80 minutes, and there is a train every 30 minutes. The Hotel Papi is 10-15 minutes walking from the train station.
Info: Rodalies Generalitat de Catalunya