delphi2009及以上版本中String与PAnsiChar转换
相关资料：
http://blog.sina.com.cn/s/blog_140f86bd70102xs49.html
在winsock编程中，使用api函数 inet_addr将ip地址转换成网络字节序时，传入参数类型为直接将string转换成PAnsiChar类型，转换出来的网络字节有错误，无法使用该ip，解决办法如下：
所有的原生字符串类型String转PAnsiChar都需要经过AnsiString过渡
strAnsi:= PAnsiChar(AnsiString(str));
其原因如下：
In D2009 and later: yes, there is. PChar is a pointer to a Char which is a unicode character (a WideChar). And PAnsiChar is a pointer to a AnsiChar, which is - as the name implies - an ANSI character.
EDIT: For pre-2009 versions of Delphi PChar and PAnsiChar are exactly the same. They both point to an (Ansi) character.
原文：https://www.cnblogs.com/FKdelphi/p/13622498.html