How to determine which port ASP.NET Core 2 is listening on when a dynamic port (0) was specified

Question

I\'ve got an ASP.NET Core 2.0 app which I intend to run as a stand-alone application. The app should start up and bind to an available port. To achieve this I configure the

Answer 1

You can use the Start() method instead of Run() to access IServerAddressesFeature at the right moment:

IWebHost webHost = new WebHostBuilder()
    .UseKestrel(options => 
         options.Listen(IPAddress.Loopback, 0)) // dynamic port
    .Build();

webHost.Start();

string address = webHost.ServerFeatures
    .Get<IServerAddressesFeature>()
    .Addresses
    .First();
int port = int.Parse(address.Split(':').Last());

webHost.WaitForShutdown();

Answer 2

I was able to do it in the StartUp.cs using the following code:

int Url = new System.Uri(Configuration["urls"]).Port;

Answer 3

I'm able to do it using reflection (ugh!). I've registered an IHostedService and injected IServer. The ListenOptions property on KestrelServerOptions is internal, therefore I need to get to it using reflection. When the hosted service is called I then extract the port using the following code:

var options = ((KestrelServer)server).Options;
var propertyInfo = options.GetType().GetProperty("ListenOptions", BindingFlags.Instance | BindingFlags.NonPublic);
var listenOptions = (List<ListenOptions>)propertyInfo.GetValue(options);
var ipEndPoint = listenOptions.First().IPEndPoint;
var port = ipEndPoint.Port;

Answer 4

At least from .Net Core 3 you can inject IServer and get the information.

using System;
using System.Linq;
using Microsoft.AspNetCore.Hosting.Server;
using Microsoft.AspNetCore.Hosting.Server.Features;

namespace MyApp.Controllers
{
    public class ServerInfoController : Controller
    {
        public ServerInfoController (IServer server)
        {
            var addresses = server.Features.Get<IServerAddressesFeature>()?.Addresses?.ToArray();
        }
    }
}

Answer 5

You can achive it in Startup class in method Configure. You can get port from ServerAddressesFeature

Here is an example of code:

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, ILogger<Startup> logger)
{
     var serverAddressesFeature = app.ServerFeatures.Get<IServerAddressesFeature>();

     loggerFactory.AddFile("logs/myfile-{Date}.txt", minimumLevel: LogLevel.Information, isJson: false);

     logger.LogInformation("Listening on the following addresses: " + string.Join(", ", serverAddressesFeature.Addresses));
}