It’s basically using a machine that can use the CF CDN port to act as a proxy for a machine that doesn’t have a CDN port.
Originally, the domain’s A or AAAA record is pointed to the reverse‑proxy machine, not the machine actually hosting the service.
On the reverse‑proxy machine, configure this domain to proxy to the IP address + port of the machine that actually provides the service.
I don’t know if this explanation is clear~
Of course, you can also choose to use EO’s CDN to directly bring the port back to the origin.
You can check my post; both CF’s origin pull and EO’s origin pull are mentioned.