I'm running a Windows Server 2016 instance on Amazon Lightsail. I have a static public IP and I've added firewall rules in Lightsail for a couple of additional ports (e.g. 123 and 321).
In IIS, I've added a website with a simple static page that is set to port 123 and any IP. I then went to Windows Firewall with Advanced Settings and added an Inbound rule for port 123.
The test page will load correctly using the local machine, and my-public-ip:123. However, when I try the same thing on a computer outside of the network, the site can't be reached. Accessing my-public-ip:80 from an external client works though. I've tried pinging the IP and alternative ports with telnet, and it's returning a connection.
I'm kind of new to IIS and I'm completely lost at this point. I imagine there's some routing or firewall rule somewhere that I need to configure but I'm just not aware of it.