• /etc/nginx/sites-enabled/upstream-43889
• Caddy Servers doest not work with backend_server_43889

# upstream backend_servers 
upstream backend_servers_43889 {
    server h2Jammy.yushei.net:43889;
    # server h2jammy-01.yushei.net:43889 weight=1;
}

server {
     server_name  munetaka.me:43889;
     charset utf-8;

     location / {
        proxy_pass http://backend_servers_43889;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto https;
        proxy_set_header X-Forwarded-Host munetaka.me;
        proxy_set_header X-Forwarded-Port 43889;
     }

     listen 43889 ssl; # managed by Certbot
     ssl_certificate /etc/letsencrypt/live/munetaka.me/fullchain.pem; # managed by Certbot
     ssl_certificate_key /etc/letsencrypt/live/munetaka.me/privkey.pem; # managed by Certbot
}

When systemctl restart nginx

Jun 07 12:51:23 pi3Nginx.munetaka.me systemd[1]: Failed to start nginx.service - A high performance web server and a reverse proxy server.
Jun 07 12:55:10 pi3Nginx.munetaka.me systemd[1]: Starting nginx.service - A high performance web server and a reverse proxy server...
Jun 07 12:55:10 pi3Nginx.munetaka.me nginx[2319]: 2024/06/07 12:55:10 [emerg] 2319#2319: duplicate upstream "backend_servers" in /etc/nginx/sites-enabled/upstream-43889:4
Jun 07 12:55:10 pi3Nginx.munetaka.me nginx[2319]: nginx: configuration file /etc/nginx/nginx.conf test failed
Jun 07 12:55:10 pi3Nginx.munetaka.me systemd[1]: nginx.service: Control process exited, code=exited, status=1/FAILURE
Jun 07 12:55:10 pi3Nginx.munetaka.me systemd[1]: nginx.service: Failed with result 'exit-code'.