This technology allows you to redirect calls to port 80 or 443 to different services that could be running in one or many computers in a network. This way, you could connect to let’s say jellyfin, running on por 8096 from a specific url and also to something else, like a blog, running on port 8001, even if this services are running on the same machine with the same IP.
When you access a website through the proxy, the proxy server receives the request and then forwards it to the corresponding service on your server. But how does the proxy know which service to forward the request to? The answer lies in the HTTP Host header. When you access a website, your browser sends an HTTP request to the server, which includes a Host header that specifies the domain name of the website you’re trying to access. For example, if you access jellyfin.mydomain.com, the Host header would contain the value jellyfin.mydomain.com. The proxy server (NGINX, in this case) receives this request and checks the Host header to determine which service to forward the request to. This is known as virtual hosting. In the NGINX configuration file, you specify the server_name directive to match the domain name of the incoming request. For example:
For this setup I’ve used Nginx Proxy Manager, since it makes the configuration of Nginx a lot easier with a GUI front.
I’m initially running jellyfin on a docker container on port 28096 and I want to be able to access it from a subdomain jellyfin.migueldeoleiros.com
I created a new proxy host with that information, and opened the ports 80 and 443 on my router. I also needed to create the subdomain pointing to the public IP on my domain register (in this case namecheap.com)
Right off the bat this works with HTTP already, but NPM makes it trivial to add SSL certificates, so you can create one for the subdomain in question and add it to the host, setting it to force ssl and now the page work over HTTPS.
In the case of jellyfin there are some specific configs that I grabed from their wiki page. Although jellyfin has some config options in apps for https this were not needed when using NPM to configure SSL.