Using Kestrel you can specify port using next approaches:

1. Defining ASPNETCORE_URLS environment variable.

   Windows

   SET ASPNETCORE_URLS=https://0.0.0.0:5001
   

   OS X

   export ASPNETCORE_URLS=https://0.0.0.0:5001
   

2. Via command line passing --server.urls parameter

   dotnet run --server.urls=http://0.0.0.0:5001
   

3. Using UseUrls() method

   var builder = new WebHostBuilder()
                 .UseKestrel()
                 .UseUrls("http://0.0.0.0:5001")
   

4. Defining server.urls setting in configuration source.

Next sample use hosting.json file for example.

Add `hosting.json` with the following content to you project:

    {
       "server.urls": "http://<ip address>:<port>" 
    }

Examples of posible values:

• listen 5000 on any IP4 and IP6 addresses from any interface:

   "server.urls": "http://*:5000" 
  

  or

   "server.urls": "http://::5000;http://0.0.0.0:5000"
  

• listen 5000 on every IP4 address:

   "server.urls": "http://0.0.0.0:5000"
  

One should be carefully and not use http://*:5000;http://::5000, http://::5000;http://*:5000, http://*:5000;http://0.0.0.0:5000 or http://*:5000;http://0.0.0.0:5000 because it will require to register IP6 address :: or IP4 address 0.0.0.0 twice

Add file to publishOptions in project.json

"publishOptions": {
"include": [
    "hosting.json",
    ...
  ]
}

and in entry point for the application call .UseConfiguration(config) when creating WebHostBuilder:

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

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

    host.Run();
}