SimpleTestServer.cs

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

namespace SimpleTestServer_DotNet
{
    public static class SimpleTestServer
    {
        public static void Main(string[] args) =>
            WebHost.CreateDefaultBuilder(args).UseStartup<Startup>().Build().Run();
    }

    public class Startup
    {
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            app.Run(async context =>
            {
                context.Response.Headers.Add("Content-Type", "application/json");
                await context.Response.WriteAsync("{ \"path\":\"" + context.Request.Path + "\" }");
            });
        }
    }
}