I want my App Engine project to be able to receive/handle traffic that comes in from a custom port (i.e. https://www.my-appengine-project.com:12999/some-endpoint)
I'm currently using a Google Cloud external HTTPS Load Balancer, but it seems that you can only configure it to receive traffic on port 443.
https://cloud.google.com/load-balancing/docs/forwarding-rule-concepts#port_specifications
What can I do to make this work? I need to receive traffic on a specific port.