呵呵,找到正解,原文如下:
When using these functions we do not care about the actual values ( big endian or little endian ) for the host byte order and the network byte order. What we must do is be certain to call the appropriate function to convert a given value between the host and network byte order. ON THOSE SYSTERMS THAT HAVE THE SAME BYTE ORDERING AS THE INTERNET PROTOCOLS ( BIG ENDIAN ), THESE FOUR FUNCTIONS ARE USUALLY DEFINED AS NULL MACROS.
原文来自《Unix Network Programming Vol 1》 Second Edition, by Richard Stevens, Page 82