No app can accept casts. When your are using Google Cast, you don't stream from your device to the TV/Chromecast. Your device sends a package containing the ap

No app can accept casts. When your are using Google Cast, you don't stream from your device to the TV/Chromecast. Your device sends a package containing the app name you want to open and some basic configuration data and then the TV/Chromecast downloads a web app from Google's severs and opens it with the configuration you provided. Then your device can interact with it.