One embodiment of the present invention relates to a method by which a first device for supporting a WiFi direct service establishes a session, the method including: causing an application service platform (ASP) layer to receive an Advertise Service method from a service layer; causing the ASP layer to receive a REQUEST_SESSION message from a second device; causing the ASP layer to receive a SetSessionReady method from the service layer; and causing the ASP layer to transmit an ADDED_SESSION message to the second device in response to the REQUEST_SESSION message, wherein each of the AdvertiseService method, the REQUEST_SESSION message, and the ADDED_SESSION message includes port information, and the port information included in the AdvertiseService method is the same as the port information included in the ADDED_SESSION message when the first device gives, to the second device, the port information related to the session.