After integrating the first chunk of IPv6 changes, Tim Peters quickly found that they won't compile on Windows - even though this was the least-critical part of the patch. Specifically, this code emulates the getaddrinfo and getnameinfo calls, which will be exposed to Python programs in a later patch. Therefore, it is essential that they are available on every system, either directly or through emulation. For Windows, one option is to use the Microsoft-provided emulation, which is available from http://msdn.microsoft.com/downloads/sdks/platform/tpipv6.asp To use this emulation, only the header files of the package are required; it is not necessary to actually install the IPv6 preview on the system. The MS emulation will try to load a few DLLs which are known to provide getaddrinfo. If neither DLL is found, the code in the header file falls back to an emulation. That way, the resulting socket.pyd would use the true API function on installations that provide them, and the emulation on all other systems. The only requirement for building Python is then that the header file from the technology preview is available on the build machine (tpipv6.h). It may be that the header file is also included in recent SDK releases, I haven't checked. Is such a requirement acceptable for building the socket module on Windows? Regards, Martin