Socket::GetAddrInfo(3)User Contributed Perl DocumentatioSocket::GetAddrInfo(3)NAME
"Socket::GetAddrInfo" - RFC 2553's "getaddrinfo" and "getnameinfo"
functions.
SYNOPSIS
use Socket qw( SOCK_STREAM );
use Socket::GetAddrInfo qw( :newapi getaddrinfo getnameinfo );
use IO::Socket;
my $sock;
my %hints = ( socktype => SOCK_STREAM );
my ( $err, @res ) = getaddrinfo( "www.google.com", "www", \%hints );
die "Cannot resolve name - $err" if $err;
while( my $ai = shift @res ) {
$sock = IO::Socket->new();
$sock->socket( $ai->{family}, $ai->{socktype}, $ai->{protocol} ) or
undef $sock, next;
$sock->connect( $ai->{addr} ) or undef $sock, next;
last;
}
if( $sock ) {
my ( $err, $host, $service ) = getnameinfo( $sock->peername );
print "Connected to $host:$service\n" if !$err;
}
DESCRIPTION
The RFC 2553 functions "getaddrinfo" and "getnameinfo" provide an
abstracted way to convert between a pair of host name/service name and
socket addresses, or vice versa. "getaddrinfo" converts names into a
set of arguments to pass to the "socket()" and "connect()" syscalls,
and "getnameinfo" converts a socket address back into its host
name/service name pair.
These functions provide a useful interface for performing either of
these name resolution operation, without having to deal with IPv4/IPv6
transparency, or whether the underlying host can support IPv6 at all,
or other such issues. However, not all platforms can support the
underlying calls at the C layer, which means a dilema for authors
wishing to write forward-compatible code. Either to support these
functions, and cause the code not to work on older platforms, or stick
to the older "legacy" resolvers such as "gethostbyname()", which means
the code becomes more portable.
This module attempts to solve this problem, by detecting at compiletime
whether the underlying OS will support these functions. If it does not,
the module will use pure-perl emulations of the functions using the
legacy resolver functions instead. The emulations support the same
interface as the real functions, and behave as close as is resonably
possible to emulate using the legacy resolvers. See
Socket::GetAddrInfo::Emul for details on the limits of this emulation.
As of "Socket" version 1.93 (as shipped by Perl version 5.13.9, and
hopefully will be in 5.14), core Perl already supports "getaddrinfo".
On such a system, this module simply uses the functions provided by
"Socket", and does not need to use its own compiled XS, or pure-perl
legacy emulation.
EXPORT TAGS
The following tags may be imported by "use Socket::GetAddrInfo qw( :tag
)":
AI Imports all of the "AI_*" constants for "getaddrinfo" flags
NI Imports all of the "NI_*" constants for "getnameinfo" flags
EAI Imports all of the "EAI_*" for error values
constants
Imports all of the above constants
FUNCTIONS
( $err, @res ) = getaddrinfo( $host, $service, $hints )
When given both host and service, this function attempts to resolve the
host name to a set of network addresses, and the service name into a
protocol and port number, and then returns a list of address structures
suitable to connect() to it.
When given just a host name, this function attempts to resolve it to a
set of network addresses, and then returns a list of these addresses in
the returned structures.
When given just a service name, this function attempts to resolve it to
a protocol and port number, and then returns a list of address
structures that represent it suitable to bind() to.
When given neither name, it generates an error.
The optional $hints parameter can be passed a HASH reference to
indicate how the results are generated. It may contain any of the
following four fields:
flags => INT
A bitfield containing "AI_*" constants
family => INT
Restrict to only generating addresses in this address family
socktype => INT
Restrict to only generating addresses of this socket type
protocol => INT
Restrict to only generating addresses for this protocol
Errors are indicated by the $err value returned; which will be non-zero
in numeric context, and contain a string error message as a string. The
value can be compared against any of the "EAI_*" constants to determine
what the error is.
If no error occurs, @res will contain HASH references, each
representing one address. It will contain the following five fields:
family => INT
The address family (e.g. AF_INET)
socktype => INT
The socket type (e.g. SOCK_STREAM)
protocol => INT
The protocol (e.g. IPPROTO_TCP)
addr => STRING
The address in a packed string (such as would be returned by
pack_sockaddr_in)
canonname => STRING
The canonical name for the host if the "AI_CANONNAME" flag was
provided, or "undef" otherwise. This field will only be present
on the first returned address.
( $err, $host, $service ) = getnameinfo( $addr, $flags )
This function attempts to resolve the given socket address into a pair
of host and service names.
The optional $flags parameter is a bitfield containing "NI_*"
constants.
Errors are indicated by the $err value returned; which will be non-zero
in numeric context, and contain a string error message as a string. The
value can be compared against any of the "EAI_*" constants to determine
what the error is.
BUGS
· At the time of writing, there are no test reports from the
"MSWin32" platform either PASS or FAIL. I suspect the code will not
currently work as it stands on that platform, but it should be
fairly easy to fix, as "Socket6" is known to work there. Patches
welcomed. :)
SEE ALSO
· <http://tools.ietf.org/html/rfc2553> - Basic Socket Interface
Extensions for IPv6
ACKNOWLEDGEMENTS
Christian Hansen <chansen@cpan.org> - for help with some XS features
and Win32 build fixes.
Zefram <zefram@fysh.org> - for help with fixing some bugs in the XS
code.
Reini Urban <rurban@cpan.org> - for help with older perls and more
Win32 build fixes.
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
perl v5.18.2 2014-05-14 Socket::GetAddrInfo(3)
