The "Can Not Connect GameServer !!" error is programmed inside the Client.exe
You need to run launcher with same IP as GS and LS to login or you get this error.
If you want to completely remove this error, you can use OllyDbg and JMP the function that calls the IP check and error message.
Here's a picture of what you need to do:
After you edit this, save to binary and that's it.
- - - Updated - - -
Updated the first post with the Launcher source code.
Link:
https://github.com/phant0m-dg/LauncherRXJH