How to specify the port an ASP.NET Core application is hosted on?

In ASP.NET Core 3.1, there are 4 main ways to specify a custom port:

Using command line arguments, by starting your .NET application with --urls=[url]:

dotnet run --urls=http://localhost:5001/

Using appsettings.json, by adding a Urls node:

{
  "Urls": "http://localhost:5001"
}

Using environment variables, with ASPNETCORE_URLS=http://localhost:5001/.

Using UseUrls(), if you prefer doing it programmatically:

public static class Program
{
    public static void Main(string[] args) =>
        CreateHostBuilder(args).Build().Run();

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(builder =>
            {
                builder.UseStartup<Startup>();
                builder.UseUrls("http://localhost:5001/");
            });
}

Or, if you're still using the web host builder instead of the generic host builder:

public class Program
{
    public static void Main(string[] args) =>
        new WebHostBuilder()
            .UseKestrel()
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseIISIntegration()
            .UseStartup<Startup>()
            .UseUrls("http://localhost:5001/")
            .Build()
            .Run();
}

---

You can insert Kestrel section in asp.net core 2.1+ appsettings.json file.

  "Kestrel": {
    "EndPoints": {
      "Http": {
        "Url": "http://0.0.0.0:5002"
      }
    }
  },

if you have not kestrel section,you can use "urls":

{
    "urls":"http://*.6001;https://*.6002"
}

but if you have kestrel in appsettings.json, urls section will failure.

---

Follow up answer to help anyone doing this with the VS docker integration. I needed to change to port 8080 to run using the "flexible" environment in google appengine.

You'll need the following in your Dockerfile:

ENV ASPNETCORE_URLS=http://+:8080
EXPOSE 8080

and you'll need to modify the port in docker-compose.yml as well:

    ports:
      - "8080"

---

You can specify hosting URL without any changes to your app.

Create a Properties/launchSettings.json file in your project directory and fill it with something like this:

{
  "profiles": {
    "MyApp1-Dev": {
        "commandName": "Project",
        "environmentVariables": {
            "ASPNETCORE_ENVIRONMENT": "Development"
        },
        "applicationUrl": "http://localhost:5001/"
    }
  }
}

dotnet run command should pick your launchSettings.json file and will display it in the console:

C:\ProjectPath [master ≡]
λ  dotnet run
Using launch settings from C:\ProjectPath\Properties\launchSettings.json...
Hosting environment: Development
Content root path: C:\ProjectPath
Now listening on: http://localhost:5001
Application started. Press Ctrl+C to shut down. 

More details: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/environments

---

Alternative solution is to use a hosting.json in the root of the project.

{
  "urls": "http://localhost:60000"
}

And then in Program.cs

public static void Main(string[] args)
{
    var config = new ConfigurationBuilder()
        .SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile("hosting.json", true)
        .Build();

    var host = new WebHostBuilder()
        .UseKestrel(options => options.AddServerHeader = false)
        .UseConfiguration(config)
        .UseContentRoot(Directory.GetCurrentDirectory())
        .UseIISIntegration()
        .UseStartup<Startup>()
        .Build();

    host.Run();
}

---

If using dotnet run

dotnet run --urls="http://localhost:5001"

---

Above .net core 2.2 the method Main support args with WebHost.CreateDefaultBuilder(args)

public class Program
{
    public static void Main(string[] args)
    {
        CreateWebHostBuilder(args).Build().Run();
    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>();
}

You can build your project and go to bin run command like this

dotnet <yours>.dll --urls=http://0.0.0.0:5001

or with multi-urls

dotnet <yours>.dll --urls="http://0.0.0.0:5001;https://0.0.0.0:5002"

Edit 2021/09/14

After .net core 3.1 you can change the file appsettings.json in the project, Config section Urls and Kestrel all works. And you can use either. Urls will easier.

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "MicrosoftHostingLifetime": "Information"
    }
  },
  "Urls": "http://0.0.0.0:5002",
  //"Kestrel": {
  //  "EndPoints": {
  //    "Http": {
  //      "Url": "http://0.0.0.0:5000"
  //    },
  //    "Https": {
  //      "Url": "https://0.0.0.0:5001"
  //    }
  //  }
  //},
  "AllowedHosts": "*"
}

Use http://0.0.0.0:5000 can access the webserver from remote connect, If you set to http://localhost:5000 that will access only in your computer.

To make Kestrel setting works, you shoud change code in Program.cs in the project.

        public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.ConfigureServices((context, services) =>
                 {
                     services.Configure<Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerOptions>(context.Configuration.GetSection("Kestrel"));
                 });
                webBuilder.UseStartup<Startup>();
            });

---

When hosted in docker containers (linux version for me), you might get a 'Connection Refused' message. In that case you can use IP address 0.0.0.0 which means "all IP addresses on this machine" instead of the localhost loopback to fix the port forwarding.

public class Program
{
    public static void Main(string[] args)
    {
        var host = new WebHostBuilder()
            .UseKestrel()
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseIISIntegration()
            .UseStartup<Startup>()
            .UseUrls("http://0.0.0.0:5000/")
            .Build();

        host.Run();
    }
}

---

On .Net Core 3.1 just follow Microsoft Doc that it is pretty simple: kestrel-aspnetcore-3.1

To summarize:

Add the below ConfigureServices section to CreateDefaultBuilder on Program.cs: // using Microsoft.Extensions.DependencyInjection; public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args) .ConfigureServices((context, services) => { services.Configure( context.Configuration.GetSection("Kestrel")); }) .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup(); }); Add the below basic config to appsettings.json file (more config options on Microsoft article): "Kestrel": { "EndPoints": { "Http": { "Url": "http://0.0.0.0:5002" } } } Open CMD or Console on your project Publish/Debug/Release binaries folder and run: dotnet YourProject.dll Enjoy exploring your site/api at your http://localhost:5002

---

Alternatively, you can specify port by running app via command line.

Simply run command:

dotnet run --server.urls http://localhost:5001

Note: Where 5001 is the port you want to run on.

---

Go to properties/launchSettings.json and find your appname and under this, find applicationUrl. you will see, it is running localhost:5000, change it to whatever you want. and then run dotnet run...... hurrah

---

I fixed the port issue in Net core 3.1 by using the following

In the Program.cs

public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args).Build().Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args)
        .ConfigureWebHost(x => x.UseUrls("https://localhost:4000", "http://localhost:4001"))
        .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); });
}

You can access the application using

http://localhost:4000

https://localhost:4001

---