If you would use UTF-8 or UTF-16, then there shouldn't be any problem at all, as they are platform universal, and independent of system settings.
But if you're using ANSI(EUC-KR, Korean) multi-byte encoding, then I think results depend on which codepage is currently set in the operating system (on both server and client).
I don't recommend using multi-byte encoding.
I recommend using UTF-8 or UTF-16.
So do I understand correctly that you're using a non-EE server appplication that sends text messages via sockets. And then try to receive those messages on EE client application, and read/decode the text messages?
The engine has functions for encoding/decoding UTF8 strings:
They are currently private (in the engine headers)
They are inside "#ifdef EE_PRIVATE"
So when you run "Esenthel Builder" and "Create Code Editor.dat" function, the function declarations don't get copied to Esenthel Code Editor.
But you can copy the functions manually to your project, if it solves your problem, then I can make the functions public, so they are always available in the Code Editor.
But if your server is also an EE based application, then you can just use Str8 or Str, and save them into File this way: