i know when i installed apache, it sets up port 8080 to take stuff in.
explanation (again, keep in mind i just learned this stuff so it might not be completely accurate):
whenever you see http://something you are automatically going to port 80 of that machine. so if you go http://yourServerIP/ it will boomerang a message out, which will come back into your port 80. If your ip is hosting server, then it takes incoming port 80 and sends it to whatever port you specified when installing your webserver. I hope that helps at least to point you in right direction.