Does anyone know if certain ports are blocked by default, even when you open them in NAT?

Got a client who has a device that broadcasts over port 4840.
If you connect to the router using SSLVPN it works perfectly, but opening the port to the device, never works.

Wasn't sure if certain ports are always blocked regardless

Hello

It depends on the type of application, when you say broadcast, what do you mean? When you VPN in, you are "in"the network so you can reach the device as if you were local. When you open ports, it may not be the same depending on the configuration of that device