Where is a container's ServicePort defined when publishing a container from Visual Studio 2022?

Question

I have published a Linux container to an Azure Container App using the publishing UI embedded within Visual Studio 2022. This seems to work and a new container image is uploaded into my Azure container registry and then loaded into the Azure Container App.

My objective is to be able to invoke a C# coded gRPC service hosted within the Azure Container App from a gRPC client test project running on my development desktop.

The test client gRPC calls are failing with the exception:

Grpc.Core.RpcException: 'Status(StatusCode="Unavailable", Detail="upstream connect error or disconnect/reset before headers.

I have configured Envoy in the Azure portal to allow external traffic and so my first diagnosis step is to ensure the container hosting the gRPC service is listening on the correct port number.

How can I verify what port my gRPC service should listen on? Here is the current code:

app.MapGrpcService<PingPongService>().RequireHost( "*:443" );