For this type of problem, I recommend doing these procedures:
Step 1:
I'm not sure, but in some cases it is necessary to check the client's "neuz.ini" file and try to set the 'ip' if it is not set correctly, or vice versa, leave it empty if it is already set.
Step 2:
Start all servers executables (7 in total)
Go to
https://canyouseeme.org/
on "Port to Check" type one of your ports and check (test all user defined ports, but you reallly just need focus on 2 ports ... PN_LOGINSRVR and PN_CERTIFIER)
If any port is not detected(mainly the 2 mentioned above) , double check your firewall , and configured ports/ips
For a quick test, you could disable your firewall(s) and try again. This way you can be sure if it is some firewall software blocking it or some IP/port configuration error.
Remember to re-enable your firewalls!
Step3:
I generally recommend avoiding using the loopback interface (ip 127.0.0.1) together with other IPs (whether local or external network), especially for those who are not used to it, and are not sure if the server source code (regardless of whether it is Flyff or any other) created a listener using INADDR_ANY or not.
So...
I initially advise changing ALL "127.0.0.1" to the IP you will use, preferably your public IP.
Repeat step 2 until all servers are identified (remembering that we usually only need to focus on 2 main ones).
Step 4:
Once you are sure that all IPs/ports are public and functional...
It's time to try to connect the client.
You can try checking step 1 again if the client does not connect.
If from that moment on everything connected normally, I used to do the reverse procedure, which is to re-enable the firewall, test, change the IP of one of the servers back to "127.0.0.1", and test... whenever it stops working, we know that we have to use an external IP and/or modify the firewall.