HttpListener Access Denied

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I am writing an HTTP server in C#.

When I try to execute the function HttpListener.Start() I get an HttpListenerException saying

"Access Denied".

When I run the app in admin mode in windows 7 it works fine.

Can I make it run without admin mode? if yes how? If not how can I make the app change to admin mode after start running?

using System;
using System.Net;

namespace ConsoleApplication1
{
    class Program
    {
        private HttpListener httpListener = null;

        static void Main(string[] args)
        {
            Program p = new Program();
            p.Server();
        }

        public void Server()
        {
            this.httpListener = new HttpListener();

            if (httpListener.IsListening)
                throw new InvalidOperationException("Server is currently running.");

            httpListener.Prefixes.Clear();
            httpListener.Prefixes.Add("http://*:4444/");

            try
            {
                httpListener.Start(); //Throws Exception
            }
            catch (HttpListenerException ex)
            {
                if (ex.Message.Contains("Access is denied"))
                {
                    return;
                }
                else
                {
                    throw;
                }
            }
        }
    }
}
12 Answers

I also faced similar problem.If you have already reserved url then you have to first delete the url to run in non admin mode else it will fail with Access is Denied error.

netsh http delete urlacl url=http://+:80

Thanks all, it was of great help. Just to add more [from MS page]:

Warning

Top-level wildcard bindings (http://*:8080/ and http://+:8080) should not be used. Top-level wildcard bindings can open up your app to security vulnerabilities. This applies to both strong and weak wildcards. Use explicit host names rather than wildcards. Subdomain wildcard binding (for example, *.mysub.com) doesn't have this security risk if you control the entire parent domain (as opposed to *.com, which is vulnerable). See rfc7230 section-5.4 for more information.

Unfortunately, for some reasons probably linked with HTTPS and certificates, the native .NET HttpListener requires admin privileges, and even for HTTP only protocol...

The good point

It is interesting to note that HTTP protocol is on top of TCP protocol, but launching a C# TCP listener doesn't require any admin privileges to run. In other words, it is conceptually possible to implement an HTTP server which do not requires admin privileges.

Alternative

Below, an example of project which doesn't require admin privileges: https://github.com/EmilianoElMariachi/ElMariachi.Http.Server

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