Paul Evans


Socket::GetAddrInfo::Emul - Pure Perl emulation of getaddrinfo and getnameinfo using IPv4-only legacy resolvers


Socket::GetAddrInfo attempts to provide the getaddrinfo and getnameinfo functions by some XS code that calls the real functions in libc. If for some reason this cannot be done; either there is no C compiler, or libc does not provide these functions, then they will be emulated using the legacy resolvers gethostbyname, etc... These emulations are not a complete replacement of the real functions, because they only support IPv4 (the AF_INET socket family). In this case, the following restrictions will apply.


  • If the family hint is supplied, it must be AF_INET. Any other value will result in an error thrown by croak.

  • The only supported flags hint values are AI_PASSIVE, AI_CANONNAME, AI_NUMERICSERV and AI_NUMERICHOST.

    The flags AI_V4MAPPED and AI_ALL are recognised but ignored, as they do not apply to AF_INET lookups. Since this function only returns AF_INET addresses, it does not need to probe the system for configured addresses in other families, so the AI_ADDRCONFIG flag is also ignored.

    Note that AI_NUMERICSERV is an extension not defined by RFC 2553, but is provided by most OSes. It is possible (though unlikely) that even the native XS implementation does not recognise this constant.


  • If the sockaddr family of $addr is anything other than AF_INET, an error will be thrown with croak.

  • The only supported $flags values are NI_NUMERICHOST, NI_NUMERICSERV, NI_NOFQDN, NI_NAMEREQD and NI_DGRAM.


This pure-perl emulation provides the IDN constants such as AI_IDN and NI_IDN, but the getaddrinfo and getnameinfo functions will croak if passed these flags. This should allow a program to probe for their support, and fall back to some other behaviour instead.


Paul Evans <>