Why can an application only listen on one port?

Question

Computer networks

Actually, the answer is not in the style: "because it's done that way", but an explanation of the reason.

Answer 1

because without a port it will not be an application
and there can be more than one
proxy listening at least 3, and even more on holidays

Answer 2

How many times in the application in the code listen is called for sockets, so many ports will listen, at least 65k, until the failed system sends

Answer 3

Because scuba. A competent question contains half of the answer :) In general, an abstract application, as Valentin correctly noted, can listen to at least all 65535 ports, there are no restrictions on this. And a certain specific application - because it was programmed that way - to listen to one port and did not assume the possibility of changing it.