newer cameras often offer a cloud service that sends data out of your home (no setup needed because it's like anyone surfing the web going out).
their clients contact their servers and either punch a hole into your internal network and/or fetch data off their servers.
see my blog on why I'm not a fan.
https://hit-mob.com/2017/11/16/secure-y ... vr-or-dvr/my app prefers to contact cameras DIRECTLY which means you need to setup port forwarding to allow access to your camera from outside.
see:
https://hit-mob.com/ip-cam-viewer-android/faq/#2an optional but recommended step is to actually forward traffic to a raspberry pi that runs stunnel, which adds ssl and controls access to all internal IOT devices (so only stunnel is accessible from outside).
https://hit-mob.com/2017/11/16/secure-y ... vr-or-dvr/