Ports are not used up by connections. One port can support 65K simultaneous connections from a single IP. If a thousand machines connect, each with their own IP, one port can handle 65 million connections. If you decide to accept HTTP requests on all ports, then each port of your 65K ports supports millions of connections or more. Suddenly you're talking about a total of billions or trillions of connections all going to one machine. And that's still only using a thousand machines to connect. Open up to the entire internet and you can push that to quintillions of theoretically possible simultaneous connections.
