No, that is not how this works, at all. First, let's go ahead and address the idea that "if the firewall blocks it, the app breaks, so it's the firewall's fault": It's not. If the firewall has not been opened, that just means it can't be accessed by remote systems until you EXPLICITLY open that port, with the correct protocol, on your firewall. That's FINE. That's how it's designed to work. There's nothing wrong with that. This means that the system administrator (or owner, if this is some individual's personal system) must allow the port to be accessed remotely, before the app can be reached remotely, increasing the security of the system.