Wait, doesn’t the Photon use a cellular connection? That will not go through your router. EDIT nope, that is the electron 
But as for Local Server (if you use one) and ports… A bit of a read, but this will shed some light
I open ports 9443 and 8080 both redirected to my Local Server and it handles the device connections.
But I imagine having the port 8080 directed to the IP of the device in question might be required with Cloud Server?? Not sure as I don’t use the cloud server when away from my local network, I connect back to my server.