He missed Hogwarts so much it was like having a constant stomach ache.  He missed the castle, with its secret passageways and ghosts,  his classes,  the mail arriving by owl, eating banquets in the Great Hall, sleeping in his four-poster bed in the tower dormitory, visiting the gamekeeper, Hagrid, in his cabin next to the Forbidden Forest in the grounds, and, especially, Quidditch, the most popular sport in the wizarding world. But more than anything else Harry missed his best friends.