A method of communication applied in a mobile terminal for projecting a file or content onto a display device through a set-top box (STB). The mobile terminal sends a request packet for requesting or triggering the STB to generate and display first identification information in a display area. When the first identification information displayed is scanned, and second identification information, should be identical to or should correspond to the first identification information, is generated by the STB. A comparison between the first identification information and the second identification information establishes authenticity and thus the identity of the sending mobile terminal, and the file or the content in the mobile terminal is then projected onto the display area of the correct display device through the STB. A second communication method, a mobile terminal, and a set-top box are also disclosed.