Remote Network Connectivity Documentation

Is there a whitepaper available that describes the methods used for providing remote (internet) connectivity to the NVR or individual cameras? I am concerned about what ports need to be open and how the session is established with the equipment. I suspect the NVR or cameras communicate with a remote reolink resource periodically and then the established TCP session is used to communicate back into the private network. Any details you could provide would be greatly appreciated.

Reolink

Reolink NVR and cameras are developed by the latest P2P tech,which does not need users to do any port forwarding or setup in router to get them online in internet.
Reolink provides its own app.(Reolink), and client(Reolink Client) to do remote access for its products. 3 steps to get them online:
Download app.->Scan QR code sticked on the product->Create Pa*sword. You are done when you confirm.

Reolink Camera connectivity in internet via router:
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Reolink NVR connectivity in internet via router:

I understand that and have this working but I am looking for a more technical explanation about how the external session is established with the equipment. There is something that is mapping the UID of the device to my external IP address to start the TCP session.

Reolink

P2P tech is widely used in IM software, like MSN, skype etc. You may refer to the web link http://www.brynosaurus.com/pub/net/p2pnat/ for more detailed information.

1. Reolink cameras and NVR support P2P function and user can easily access cameras after scan QRCode. To Support P2P, IP camera need to constantly send heart-beat packets to P2P server in Amazon AWS to keep UDP session.

2. Some users concern about the security and don't like this function. So, we released a new firmware V0428 for update.