Example of NGINX implementation for forwarddomain.net

forward-domain-nginx.conf

user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;

include /usr/share/nginx/modules/*.conf;

events {
    worker_connections  1024;
}
stream {
    upstream main {
        server 167.172.5.31:6443;
    }
    upstream forwarder {
        server 167.172.5.31:5443;
    }

    map $ssl_preread_server_name $upstream {
        s.forwarddomain.net main;
        default forwarder;
    }

    server {
        listen 167.172.5.31:443;
        listen [2400:6180:0000:00D0:0000:0000:0E08:A001]:443;
        resolver 1.1.1.1;
        proxy_pass $upstream;
        ssl_preread on;
    }
}
http {       
    server {
        server_name _ default_server;
        listen 167.172.5.31;
        listen [2400:6180:0000:00D0:0000:0000:0E08:A001];
        location / {
            proxy_pass http://127.0.0.1:5080;
            proxy_set_header Host $host;
        }
    }
        
    server {
        server_name s.forwarddomain.net;
        listen 167.172.5.31;
        listen [2400:6180:0000:00D0:0000:0000:0E08:A001];
        location / {
            proxy_pass http://127.0.0.1:5900;
            proxy_set_header Host $host;
        }
        listen 167.172.5.31:6443 ssl;
        listen [2400:6180:0000:00D0:0000:0000:0E08:A001]:6443 ssl;
        ssl_certificate /home/s/ssl.combined;
        ssl_certificate_key /home/s/ssl.key;
    }
}