Hi @yariplus ,
the forum runs on a subdomain, because there is a Wordpress-Site on the "normal" domain, which is by a different hoster, who is the DNS-Host (http://checkdomain.de), too. The nodeBB installation is hosted by http://uberspace.de and the SSL certificate is providec by letsencrypt. As a proxy I have to use Apache 2.2. This is the reason for the private Port, because Apache 2.2 can not handle websockets. Everything worked fine till i tried to switch to https. Here is the .htaccess of the Apache:
RewriteEngine On RewriteRule ^(.*)$ http://localhost:63542/$1 [NC,P,L]
Hope there is enough information now, if not, please tell me what you need.
thanks for your help!