Self Hosted OWIN Web Service - Not Listening

Question

Issue:
When running the Web API, self hosted using OWIN, All HTTP connections are refused (no status code returned), but only on a particular test machine, not on any other machines (they all work fine).

Sample code:

public static void Main(string[] args){
    var options = new StartOptions();
    options.Urls.Add($"http://+:{port}");
    using(Microsoft.Owin.Hosting.WebApp.Start<Startup>(options)){
        Console.WriteLine("Press Enter to exit.");
        Console.ReadKey();
    }
}

Additional info:
- Running as admin eliminates urlacl as being the cause of the problem. so url port reservations are not the issue.
- Tried using various port numbers to eliminate port number conflicts.
- Making the service use + url prefix in it's baseurl eliminates other listeners intercepting the request.
- Calling localhost (and other hostnames that resolve to 127.0.0.1) eliminates firewall.
- Code has been run with debugger, no exceptions there.
- There is no entry when i run netstat for that port. (The working machines show an enrty.)

Question:
I'd like to know what the issue is with this particular machine, and how to resolve it. What do you suggest in order to achieve this?

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X-Dev X-Dev · Accepted Answer · 2020-06-11T22:41:34

She solution turns out to be something seemingly unrelated.
In the Startup class, it was trying to enter A duplicate database entry and throw an exception. However this exception was wrapped within a TargetInvocationException that was already being handled (and incorrectly consumed).
The error handling was updated and all systems are now listening on the specified port correctly.

Self Hosted OWIN Web Service - Not Listening

1 Answers