A connection is uniquely identified by (IP #1, Port #1) and (IP #2, Port #2). You can have 65535 connections (in theory) from a single client to your port 80.

A connection is uniquely identified by (IP #1, Port #1) and (IP #2, Port #2). You can have 65535 connections (in theory) from a single client to your port 80. And another 65535 from a different client to port 80 on the same server. If you're serving a bunch of different clients it's not a problem.