HTTPURLConnection端口号分配

Question

我正在使用HTTPURLConnection并想知道端口问题是如何处理的？我的意思是该类使用引擎盖下的套接字，但如何在内部分配客户端套接字的端口号？有什么想法吗？

THX

Answer 1

不是。它完全取决于操作系统。

Answer 2

When creating a socket you have to take into account whether you want to open a server-socket or a client-socket.

A server-socket is opend and sits there waiting for an incoming request to start a "conversation". So it needs a port-number that is known to the client. For this reason several services have "well-known ports" like HTTP is port 80 etc.

A client-socket is created an starts with contacting a server-socket. In this case the server does not need to know the clients port-number in advance - it will receive it with the first incoming request. So when opening a client-socket the operating system will just choose a random port from a list of unused ports (look up "ephemeral port") and often close it once the conversation is finished.

The situation is similar to ip-adresses: the client needs to know the servers ip-address to contact it but the server does not need to know each clients ip-address.