I have a server I am using to host public internet services where I want to start and stop many instances, lets say up to 50 per physical server. The architecture of the software means each instance needs its own port (unlike say HTTP where I could have a single Apache/NGINX/etc. then proxy requests to the right place based on domain name etc.).
Is there any security risk of making say 50 unprivileged ports (assuming I extend the software default port, this would be say UDP and TCP ports 35000 to 35050) permanently open in the systems and network firewalls, even when there is currently no instance running on that port? OR should I go to the extra effort to dynamically open/close the ports?
Does it matter that the software appears to default into the dynamic port range, or an unprivileged port (at least for Linux servers where low port numbers need root) in general?