File exchange between web ui app and native service app


we have one web ui application and one independent native service application running on a Gear S3 frontier (Tizen 4) and want to exchange files between them. We are able to send files from the service app to the web app using application controls. But the other way does not work. If we call from the web app the service app we get either a permission error (if explicitly) or an application not found error (if implicitly).

I saw that it is not allowed anymore to call explicitly application controls of service apps.
Is it also not allowed to call implicitly application controls of service apps?

What is a good way to send a file from a web ui app to a native service app?


Edited by: Binder on 11 Sep, 2019