503 Error when using NancyFx with Owin - owin

Question

I'm trying to use NancyFx in combination with SignalR. In order to host both, I'm using Microsoft Owin. But unfortunately I always get an 503 (Service unavailable), when trying to access the REST-API via PostMen (REST-Api Client extension for chromium browsers). So I extracted the main ingredients to a more simple program, that allows me to switch between Nancy Selfhost and Owin.
When using Nancy SelfHost, everything works fine, but using Owin I still got a 503 error.
internal class Program {
private const bool _USE_SELF_HOST = false;
private static void Main(string[] args) {
if (_USE_SELF_HOST) {
var host = "http://localhost:7084";
UseSelfHost(host);
} else {
var host = "http://localhost:7084";
UsingWebApp(host);
}
}
private static void UseSelfHost(string host) {
var webhost = new NancyHost(new Uri(host));
webhost.Start();
Console.ReadLine();
webhost.Stop();
}
private static void UsingWebApp(string host) {
var nancyHost = WebApp.Start<Startup>(host);
Console.WriteLine($"Nancy started at {host}");
Console.ReadLine();
nancyHost.Dispose();
}
}
public class MainModule : NancyModule {
public MainModule() {
Get["/"] = x => "Hello world!";
}
}
I checked:
netsh http show urlacl - I'm allowed to open this port
Visual Studio is running with Admin rights, besides this should not be needed.

Answer 1

A colleague of mine found an error in my netsh configuration. I had two urlacls for the same tcp port:
Reservierte URL : http://wks-user:7084/
Benutzer: DOMAIN\user
Abh▒ren: Yes
Delegieren: No
SDDL: D:(A;;GX;;;XXX)
Reservierte URL : http://+:7084/
Benutzer: DOMAIN\user
Abh▒ren: Yes
Delegieren: No
SDDL: D:(A;;GX;;;XXX)
After removing the first entry via
netsh http delete urlacl http://wks-user:7084/
everything works as expected.