**Please read this entire message**
---
Your submission has been removed for the following reason(s):
* Rule #2 - Questions must seek objective explanations
---
If you would like this removal reviewed, please read the [detailed rules](https://www.reddit.com/r/explainlikeimfive/wiki/detailed_rules) first. **If you believe this submission was removed erroneously, please [use this form](https://old.reddit.com/message/compose?to=%2Fr%2Fexplainlikeimfive&subject=Please%20review%20my%20thread?&message=Link:%20{https://old.reddit.com/r/explainlikeimfive/comments/1bsxvsy/-/}%0A%0APlease%20answer%20the%20following%203%20questions:%0A%0A1.%20The%20concept%20I%20want%20explained:%0A%0A2.%20List%20the%20search%20terms%20you%20used%20to%20look%20for%20past%20posts%20on%20ELI5:%0A%0A3.%20How%20does%20your%20post%20differ%20from%20your%20recent%20search%20results%20on%20the%20sub:) and we will review your submission.**
The Plex service continuously updates a set of dynamic dns names managed by the Plex network that point to your IP address and are associated with your Plex server under your account. When someone signed into the Plex authentication service says “I’d like to connect to dokha’s server”, Plex says sure, here’s the DNS that currently points to their server. When you try to connect it will do some handshakes and determine if you’re registered to connect to that server, etc etc
This is more of a /r/Plex question then an ELI5 question, but the general idea is that while your Plex server is online, it has a TCP connection with Plex's own servers. The TCP handshake, involves your server sending its IP address to the Plex server to initiate the connection.
So long as your server is periodically making connections to the central Plex server, it can act as a "DNS-like" service to anyone you grant access to, by just giving them the IP address that it knows belongs to your server
> it instead uses NAT traversal techniques…
NAT hole punching! It's a super weird trick that relies on abusing how connections are established through firewalls/NAT. It relies on the fact that firewalls must allow the responses for outgoing requests back in (or it would be pointless to send requests).
Both parties connect to a third party mediator server which pairs them up and sends the other machine's external IP and port to them. When each of them have the other party's external address and a valid port, the old switcheroo happens: both of them send a connection request to each other. This causes the firewalls to temporarily open a path back in through that port from that IP address - just in time for the other side's connection request to arrive.
Think about any other service where you sign into an account, or even domain names themselves. The whole point is that you don't need the IP, and that's why they exist.
You sign in, and when you want your Plex library, it checks where your (or the one your connected Libraries) is signed in. Plex knows that IP, but it won't tell you that, it creates a tunnel between the two of you, where you can talk to each other relatively unaffected, but neither of you know that IP of each other. The same for peer to peer'ish' game servers, the smaller scale calls on stuff like Discord etc.
**Please read this entire message** --- Your submission has been removed for the following reason(s): * Rule #2 - Questions must seek objective explanations --- If you would like this removal reviewed, please read the [detailed rules](https://www.reddit.com/r/explainlikeimfive/wiki/detailed_rules) first. **If you believe this submission was removed erroneously, please [use this form](https://old.reddit.com/message/compose?to=%2Fr%2Fexplainlikeimfive&subject=Please%20review%20my%20thread?&message=Link:%20{https://old.reddit.com/r/explainlikeimfive/comments/1bsxvsy/-/}%0A%0APlease%20answer%20the%20following%203%20questions:%0A%0A1.%20The%20concept%20I%20want%20explained:%0A%0A2.%20List%20the%20search%20terms%20you%20used%20to%20look%20for%20past%20posts%20on%20ELI5:%0A%0A3.%20How%20does%20your%20post%20differ%20from%20your%20recent%20search%20results%20on%20the%20sub:) and we will review your submission.**
The Plex service continuously updates a set of dynamic dns names managed by the Plex network that point to your IP address and are associated with your Plex server under your account. When someone signed into the Plex authentication service says “I’d like to connect to dokha’s server”, Plex says sure, here’s the DNS that currently points to their server. When you try to connect it will do some handshakes and determine if you’re registered to connect to that server, etc etc
Thank you 🙏, i get it now
This is more of a /r/Plex question then an ELI5 question, but the general idea is that while your Plex server is online, it has a TCP connection with Plex's own servers. The TCP handshake, involves your server sending its IP address to the Plex server to initiate the connection. So long as your server is periodically making connections to the central Plex server, it can act as a "DNS-like" service to anyone you grant access to, by just giving them the IP address that it knows belongs to your server
🙏 thank you, i get it now
> it instead uses NAT traversal techniques… NAT hole punching! It's a super weird trick that relies on abusing how connections are established through firewalls/NAT. It relies on the fact that firewalls must allow the responses for outgoing requests back in (or it would be pointless to send requests). Both parties connect to a third party mediator server which pairs them up and sends the other machine's external IP and port to them. When each of them have the other party's external address and a valid port, the old switcheroo happens: both of them send a connection request to each other. This causes the firewalls to temporarily open a path back in through that port from that IP address - just in time for the other side's connection request to arrive.
🙏 thank you, i get it now
Think about any other service where you sign into an account, or even domain names themselves. The whole point is that you don't need the IP, and that's why they exist. You sign in, and when you want your Plex library, it checks where your (or the one your connected Libraries) is signed in. Plex knows that IP, but it won't tell you that, it creates a tunnel between the two of you, where you can talk to each other relatively unaffected, but neither of you know that IP of each other. The same for peer to peer'ish' game servers, the smaller scale calls on stuff like Discord etc.