Expose particular REST controller on specific port using Spring Webflux

We have a spring boot based application and using spring webflux, we are exposing 3 ports

1. server.port
2. management.server.port (actuator) and are planning to expose another port called as admin port.

We want to expose a specific REST controller on this admin port which will be private. This api will provide all the admin level configuration and will not be available publicly to the user.

Note: We don't want to expose api on actuator port. Need to open a new port.

Using the following code to open a new port by starting a new server instance.

@Configuration
public class NettyServerForAdminPort {

    @Value("${admin.port}")
    private Integer adminPort;

    @Autowired
    HttpHandler httpHandler;

    WebServer http;

    @PostConstruct
    public void start() {
      ReactiveWebServerFactory factory = new NettyReactiveWebServerFactory(8081);
      this.http = factory.getWebServer(this.httpHandler);
      this.http.start();
    }

    @PreDestroy
    public void stop() {
      this.http.stop();
    }
}

Any insights on how this can be achieved?