Guest to Guest Communication in NAT Network

Hi, I have a nat based network.  I want to communicate between two hosts on a secure basis (not http) I have two guests, one guest is reachable to the outside internet via git.example.de. git.example.de has a DNS Entry for my supervisor. On my Supervisor I am forwarding the port 443 the respective guest. Is it possible to access a guest via its domain name (git.example.de) from a guest that is in the same network? I looked at the tcpdump, and traffic goes through to the guest, but I think its not sending anything back. When trying to curl a guest from a guest it only says: Trying 123.45.67.89:80 ... Is there anything I can do? Thank you. Best, dot