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

user_107523 0
Viewed 13048

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 WebHostBuilder to listen on "http://127.0.0.1:0" and to use the Kestrel server. Once the web host starts listening I want to save the url with the actual port in a file. I want to do this as early as possible, since another application will read the file to interact with my app.

How can I determine the port the web host is listening on?

asp.net-core-2.0 kestrel-http-server
5 Answers

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));
}
user_61970360

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();
user_13738540

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

int Url = new System.Uri(Configuration["urls"]).Port;
user_118745580

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();
        }
    }
}
user_14546580
Related