How SCADA read PLC tags from s7-1200?

Hi all..
i would like to ask about the scada and s7-1200.
currently, i'm using Integraxor scada and CPU 1212c.

in my situation,
my PLC will be at a river in order to monitor the water level.
my scada will be a the control centre.
both of them will use the GSM modem that support the port forwading.

during the demo, i set the PLC ip : 192.168.0.5
scada ip : 192.168.0.33
both of them using the same network.
on the scada, it will read the PLC tags using port 102.
it work perfectly.

now, i need to separate them and using the internet.
PLC WAN ip : 183.171.208.194
Scada WAN ip : 183.171.208.195

i already set the port forwarding in GSM modem.
and the scada need to read the PLC tags using 183.171.208.194:102

but i failed to connect it.
it said the port is not opened.

Are you sure that you internet service provider are not blocking port forwarding?

yes, i'm sure

thank you for your reply Rouan.
i'm very sure that my ISP doesn't block the port forwarding because i can use others port forwarding for cctv.