OWIN Server and building them using WebHostBuilder.

Program.cs

using System.IO;
using Microsoft.AspNetCore.Hosting;

namespace OWINHost
{
    class Program
    {
        static void Main(string[] args)
        {
            var host = new WebHostBuilder()
                 .UseKestrel()
                 .UseContentRoot(Directory.GetCurrentDirectory())
                 .UseStartup<Startup>()
                 .Build();

            host.Run();
                
        }
    }
}

Startup.cs

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Builder;


namespace OWINHost
{
    public class Startup
    {
        public void Configure(IApplicationBuilder app)
        {
            app.Run(async (context) =>
            {
                await context.Response.WriteAsync("<h1>Hello from the owin host</h1>");
            });
        }
    }
}