So, I have some idea on what a reverse proxy does and will be using nginx (with the neat proxy manager UI) for my setup.
However, I’m not completely clear what exactly I want it to do and how I cn use it to run different services on one machine. I’m especially unclear on the ports configuration … tutorials will say things like “change the listening port to xxx for that service and to port yyy for the other service”
How does this work, which ports can I use and how do I need to configure the respective services?
IPv4 version: Think of your public IP:Port as the office building, your internal IP:Port as the floor number, and reverse proxy as the reception on that floor.
(Your public IP:Port is routed to your internal IP:Port by the NAT on your router. The router knows which public port relates to which internal IP:Port due to the port forwarding rules you setup.)
IPv6 version: Think of your public IP:Port as the office, and the reverse proxy as the reception.
The following will be common to both IP protocols.
The port is usually 80 or 443, because reverse proxy is used for HTTP(S) connections, and by default those connections use the aforementioned ports.
When someone connects to your IP:Port, they ask the reverse proxy “hey, can you bring me to Mr. https://my-awesome-plex.xyz ?” and the reverse proxy will act as a middleman between that someone and the actual server that is serving that domain name.
The reverse proxy, as a middleman, forwards your requests to the server, and the server’s response is forwarded back to you by the reverse proxy too.
And just to make things complete… Why do we use reverse proxies?
To hide the identity of the actual server. This is easy to understand - you are only ever talking to the proxy, never the actual server. It’s just that your messages are continually forwarded to the actual server.
To save IP addresses. (One public address can serve multiple websites, if the actual servers are given only private IP addresses.)
To load balance. The reverse proxy can direct one to another server if the first server is overloaded. This requires a website to be served by more than one server though, and selfhosters like us never really need it.
To prevent attacks. If the reverse proxy realises that someone has been making too many connections to https://my-awesome-nas.com, the reverse proxy can reject subsequent connections. This is how Cloudflare works.
Caching. If the middleman remembers that the server responded “what is the answer to everything” with “42”, then the next time someone asks the same question again, the middleman will simply reply with the same response. This takes off the workload on the server.