Using appsettings.json to configure Kestrel listen port Dotnet core 2 preview 2

As mentioned in a comment on the accepted answer, 2.1 has support for appsettings.json, see https://blogs.msdn.microsoft.com/webdev/2018/02/02/asp-net-core-2-1-roadmap/#security

A working appsettings.json:

"Kestrel": {
  "EndPoints": {
    "Http": {
      "Url": "http://localhost:5555"
    }
  }
}

This is for a Program.cs using (created by “dotnet new webapi”):

WebHost.CreateDefaultBuilder(args)

Relevant source code in GitHub
https://github.com/aspnet/MetaPackages/blob/master/src/Microsoft.AspNetCore/WebHost.cs#L163

options.Configure(builderContext.Configuration.GetSection("Kestrel"));

and https://github.com/aspnet/MetaPackages/blob/master/src/Microsoft.AspNetCore/WebHost.cs#L169

config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)