C++游戏，国内端和国外端网络通讯不一样，怎么解决？

Question

国内端，解析XML是GB2312
国外端，解析XML是UTF8
因为国外端才支持越南文字如：Nguyên-thôn-Khách-điếm-Phượng这类带特殊字符的显示。国内端，把XML转码为UTF8，直接显示乱码，无论中文还是越南文字。并且客户端不读取解析<?xml version="1.0" encoding="UTF-8"?>这样的XML。
本想直接使用国外端登录游戏，奈何国外端的通讯和国内端不同，本人技术有限，脱壳又无进展，特向CSDN的高手求助！
·········································································分割线························································
换个问法：
如何添加进国内端的xml里面，我添加Nguyên-thôn-Khách-điếm-Phượng特殊字符变为??.
使用 Unicode编码：<!-- Nguyên-thôn-Khách-điếm-Phượng -->添加进去，客户端读取出来是方块字型乱码
求字符编码的高手帮帮我！
整崩溃了！

Answer 1

换个问法：
如何把添加进国内端的xml里面，我添加Nguyên-thôn-Khách-điếm-Phượng特殊字符变为??.
使用 Unicode编码：Nguyên-thôn-Khách-điếm-Phượng添加进去，客户端读取出来是方块字型乱码
求字符编码的高手帮帮我！
整崩溃了！