Normally I use Linux Servers for my applications. Therefore I am quite new to the firewall system of Windows Servers.
I have a C# application which needs to act as a HTTP Server. There are multiple ways of realizing this with different abstraction levels: Of course there is a
Socket library to provide very fundamental functionality. For TCP traffic there is a also a
TcpClient. Both listen on a specific port and need "Inbound Rules" defined in the Windows Firewall to be accessed from another machine (no rules needed when you only need to access it from your machine).
Then there is the
HttpListener. It does not operate on per port basis, uses URI prefixes to match requests. For example the prefix "http://*:80/" would handle all port 80 http traffic.
What really disturbs me is, that for a
HttpListener to work no rule in Windows Firewall, but an entry in urlacl is needed:
netsh http add urlacl url=http://*:80/ user=DOMAIN\user
(It is a url namespace reservation)
All three methods of realizing a http server are equally useful. The difference is that a lot less code is needed when using HttpListener.
My question is: Why is there the concept of url namespace reservation, but urls not registered can be listened to by a server nevertheless. And why can registered urls bypass firewall rules? Why is there a system like this in the first place?