General web server questions

Hi, I have never thought about that but now I am interested about few basic things behind the scenes. 1) Does webserver close connection after each request? 2) When I have more browser windows opened and all request data from some webserver, does the webserver uses some kind of standard socket communication in order to recognize which connection was requesting what? 3)What if there are more users than free ports (say 66k requesting something at the same time)

Thanks :