Treasure Island - Chapter 1

In this chapter, the captain is said to be "looking round the cover", what does that expression mean?

Also, I am not getting some of the basic details (It will sound foolish):

1) Captain rapped ("knocked" as I understand it) the inn door, but as it is an inn isn't its door supposed to be open?

2) Also, Jim's father brings the captain his beer and captain is said to be looking at the inn signboard and the cliffs. So, did Jim's father brought him beer outside the inn and didn't invite the captain inside?