How does remote viewing work without DDNS?

[stormhammer87]

I was just curious...I set up my new cameras and downloaded the Amcrest app on my phone. I read about remote viewing, via DDNS in the settings of the camera itself. I didn't do this. I was wondering how I'm able to still see the cameras on the app on the phone and on the Amcrest view site when I'm not on my home network though. How does this work?

[plusfour]

I don't know specifically how Amcrest do it since I haven't had time to set up a sniffer to check, but a standard approach is to use a rendezvous server that the internal and external devices connect to in order to set up a connection. Google "TCP hole punching" if you really want all the tech details.

[plusfour]

As a followup comment, I'm assuming they're using the Amcrest servers to handle the rendezvous, you could try blocking their IP range at your router to see if the app still works, although since AFAIK they use Amazon you might end up playing whack-a-mole trying to see which IP ranges you need to block.