Useless error message

[imperugo]

Hi,
today I had a problem deploying my aspnet core application on Azure.
The error message was saying:

Application: Gaia.Bmw.Admin.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.UvException
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.Libuv.Check(Int32)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.Libuv.tcp_bind(Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.UvTcpHandle, Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.SockAddr ByRef, Int32)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Networking.UvTcpHandle.Bind(Microsoft.AspNetCore.Server.Kestrel.ServerAddress)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.TcpListenerPrimary.CreateListenSocket()
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.Listener+<>c.<StartAsync>b__6_0(System.Object)
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(System.Threading.Tasks.Task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(System.Threading.Tasks.Task)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.ListenerPrimary+<StartAsync>d__11.MoveNext()

Exception Info: System.AggregateException
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean)
   at System.Threading.Tasks.Task.Wait(Int32, System.Threading.CancellationToken)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.KestrelEngine.CreateServer(Microsoft.AspNetCore.Server.Kestrel.ServerAddress)
   at Microsoft.AspNetCore.Server.Kestrel.KestrelServer.Start[[Microsoft.AspNetCore.Hosting.Internal.HostingApplication+Context, Microsoft.AspNetCore.Hosting, Version=1.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60]](Microsoft.AspNetCore.Hosting.Server.IHttpApplication`1<Context>)
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.Start()
   at Microsoft.AspNetCore.Hosting.WebHostExtensions.Run(Microsoft.AspNetCore.Hosting.IWebHost, System.Threading.CancellationToken, System.String)
   at Microsoft.AspNetCore.Hosting.WebHostExtensions.Run(Microsoft.AspNetCore.Hosting.IWebHost)
   at Gaia.Bmw.Admin.Program.Main(System.String[])

After few hours I noticed that the order on program.cs file was wrong.

.UseIISIntegration()must be after .UseUrls()

I don't know if it is my fault or not (for me the order wasn't so important, otherwise I should get a compilation error) but the error message wasn't helpful.

[Tratcher]

This issue was moved to aspnet/KestrelHttpServer#1020

[davidfowl]

The order is important because the ASP.NET Core module passes the port to Kestrel when running behind IIS. It's the equivalent in node when you do this:

 app.set('port', process.env.PORT || 3000);

In ASP.NET it's the reverse:

.UseUrls(...) -> // defaults
.UseIISIntegration() // override when IIS active

As for the unhelpful error message, that's a kestrel issue:

/cc @CesarBS @halter73

[imperugo]

Hi @davidfowl
thanks for the quick answer.
If the order is important, I'm not should be able to do it, right?

You can "play" with fluent interfaces to prevent this error. doesn't it?

[Tratcher]

aspnet/IISIntegration#242