Azure Web Api Jwt - Unable to obtain configuration Socket forbidden - jwt

Question

Have an Asp.Net Core 2.2.1 Web Api that is trying to obtain OpenId Configuration so that it can authenticate a request. The authority web site happens to be IdentityServer4.
The /.well-known/openid-configuration looks correct and the api site is running and unsecure api methods work ok.
Viewing the logs in Kudu, I see the following error. Appears to be caused by a Sockets issue but I have no idea what's wrong here.
All works fine locally on my dev machine, so what am I missing / is needed for Azure?
System.IO.IOException: IDX20804: Unable to retrieve document from: '[PII is hidden]'. --->
System.Net.Http.HttpRequestException: An attempt was made to access a socket
in a way forbidden by its access permissions --->
Full error detail;
2019-01-11 11:07:43.096 +00:00 [Error] Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler: Exception occurred while processing message.
System.InvalidOperationException: IDX20803: Unable to obtain configuration from: '[PII is hidden]'. ---> System.IO.IOException: IDX20804: Unable to retrieve document from: '[PII is hidden]'. ---> System.Net.Http.HttpRequestException: An attempt was made to access a socket in a way forbidden by its access permissions ---> System.Net.Sockets.SocketException: An attempt was made to access a socket in a way forbidden by its access permissions
at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken)
--- End of inner exception stack trace ---
at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken)
at System.Threading.Tasks.ValueTask`1.get_Result()
at System.Net.Http.HttpConnectionPool.CreateConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Threading.Tasks.ValueTask`1.get_Result()
at System.Net.Http.HttpConnectionPool.WaitForCreatedConnectionAsync(ValueTask`1 creationTask)
at System.Threading.Tasks.ValueTask`1.get_Result()
at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
at Microsoft.IdentityModel.Protocols.HttpDocumentRetriever.GetDocumentAsync(String address, CancellationToken cancel)
--- End of inner exception stack trace ---
at Microsoft.IdentityModel.Protocols.HttpDocumentRetriever.GetDocumentAsync(String address, CancellationToken cancel)
at Microsoft.IdentityModel.Protocols.OpenIdConnect.OpenIdConnectConfigurationRetriever.GetAsync(String address, IDocumentRetriever retriever, CancellationToken cancel)
at Microsoft.IdentityModel.Protocols.ConfigurationManager`1.GetConfigurationAsync(CancellationToken cancel)
--- End of inner exception stack trace ---
at Microsoft.IdentityModel.Protocols.ConfigurationManager`1.GetConfigurationAsync(CancellationToken cancel)
at Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler.HandleAuthenticateAsync()

Answer 1

After hours of debugging, and switching on
IdentityModelEventSource.ShowPII = true; //show detail of error and see problem
to see the problem with the well-known configuration I saw that it was not picking up application settings from the Azure portal.
As my settings were nested, I just needed to make sure the key in the Azure blade matched.
i.e.
{
"AppSettings": {
"ApiUrl": "someUrl",
"AuthorityUrl": "anotherUrl"
}, ...
becomes
AppSettings:ApiUrl
Simple mistake gotcha.