Friendly spirit saying good night

      My mom and I moved into this new house June 10, 2014. My mom told me about 2weeks ago she heard 2 distinctive knocks on our front door about 2am in the morning. She thought it was me but then realized I was in bed. She listened but heard nothing more.
      The odd thing is our screen door is very loud and can be heard all through the house. She said the screen door never made a sound, but the knocking clearly came from the door. Last night, I WS up very late on the computer well after midnight. I finally got undressed, climbed into bed, put my head on the pillow and no more than 10 seconds later, heard two loud knocks on the wall above my head.I listened but heard nothing more. It was very creepy but I ignored it.
      I remembered my mom leaves for work well before 7am. Nobody was in the house but me. I heard nothing again but the knocks were very real. They weren't scary, that's the thing. The sound exactly like what knocking on a door sounds like. I told my mom this and she said she heard the 2 knocks last night on the wall but thought it was me. My mom suggested may be its a friendly spirit saying good night and telling me get up for school.