How to setup eureka clients behind reverse proxy with different port?

I am currently trying to setup service discovery with eureka, but the clients register with the wrong port. Every Eureka client is on a different server behind its own nginx reverse proxy and it is reachable from outside via https on port 443, but the java eureka clients are configured on different port. I also tried configuring them on the same port as nginx exposes, but than the nginx server has infinited redirects and stops after some attempts with error "invalid redirect". Being on different port the eureka clients register at the server with the port configure in spring boot yaml server port config. If then a client tries to reach another client it uses the port configured in the spring boot application. I need to be able to register the eureka client on a different port than I am running the client. Is that possible? What am I missing here? Would be using Zuul as a gateway make a difference here?

Setup (every system is deployed on a different VServer behind NGINX reverse proxy):
Eureka Server
Multiple Eureka Clients (API, UI, etc)
Identity Management Keycloak SSO server not registered with eureka server

A port can only be used by one service at a time. Hence, you cannot configure nignx and spring boot to listen on the same port and receive the error message.

Spring boot does not know about the proxy setup and hence the eureka client registers the instance (with the spring.port) at the eureka server. You can configure the eurka instance with the EurekaInstanceConfig. In this case you want to change eureka.instance.port=443 to the one exposed by nginx.