Which port to open

[PeetX]

Hi,
I've got the camera-isight up and running on my mac with a webcam and ffmpeg. (webcam->ffmpeg->mac->homebridge->appletv->iphone(wifi = ok, mobile=nok)
On my internal network it's running fine. But I get the message "No Response This camera is not responding" when I open homekit on an external network (like my mobile).
Which port do I have to open? And on which device? My mac, my appletv.