Provided by: perl-doc_5.36.0-9ubuntu1.1_all 
NAME
"IO::Socket::IP" - Family-neutral IP socket supporting both IPv4 and IPv6
SYNOPSIS
use IO::Socket::IP;
my $sock = IO::Socket::IP->new(
PeerHost => "www.google.com",
PeerPort => "http",
Type => SOCK_STREAM,
) or die "Cannot construct socket - $@";
my $familyname = ( $sock->sockdomain == PF_INET6 ) ? "IPv6" :
( $sock->sockdomain == PF_INET ) ? "IPv4" :
"unknown";
printf "Connected to google via %s\n", $familyname;
DESCRIPTION
This module provides a protocol-independent way to use IPv4 and IPv6 sockets, intended as
a replacement for IO::Socket::INET. Most constructor arguments and methods are provided in
a backward-compatible way. For a list of known differences, see the "IO::Socket::INET"
INCOMPATIBILITES section below.
It uses the getaddrinfo(3) function to convert hostnames and service names or port numbers
into sets of possible addresses to connect to or listen on. This allows it to work for
IPv6 where the system supports it, while still falling back to IPv4-only on systems which
don't.
REPLACING "IO::Socket" DEFAULT BEHAVIOUR
By placing "-register" in the import list to "IO::Socket::IP", it will register itself
with IO::Socket as the class that handles "PF_INET". It will also ask to handle "PF_INET6"
as well, provided that constant is available.
Changing "IO::Socket"'s default behaviour means that calling the "IO::Socket" constructor
with either "PF_INET" or "PF_INET6" as the "Domain" parameter will yield an
"IO::Socket::IP" object.
use IO::Socket::IP -register;
my $sock = IO::Socket->new(
Domain => PF_INET6,
LocalHost => "::1",
Listen => 1,
) or die "Cannot create socket - $@\n";
print "Created a socket of type " . ref($sock) . "\n";
Note that "-register" is a global setting that applies to the entire program; it cannot be
applied only for certain callers, removed, or limited by lexical scope.
CONSTRUCTORS
new
$sock = IO::Socket::IP->new( %args )
Creates a new "IO::Socket::IP" object, containing a newly created socket handle according
to the named arguments passed. The recognised arguments are:
PeerHost => STRING
PeerService => STRING
Hostname and service name for the peer to "connect()" to. The service name may be
given as a port number, as a decimal string.
PeerAddr => STRING
PeerPort => STRING
For symmetry with the accessor methods and compatibility with "IO::Socket::INET",
these are accepted as synonyms for "PeerHost" and "PeerService" respectively.
PeerAddrInfo => ARRAY
Alternate form of specifying the peer to "connect()" to. This should be an array
of the form returned by "Socket::getaddrinfo".
This parameter takes precedence over the "Peer*", "Family", "Type" and "Proto"
arguments.
LocalHost => STRING
LocalService => STRING
Hostname and service name for the local address to "bind()" to.
LocalAddr => STRING
LocalPort => STRING
For symmetry with the accessor methods and compatibility with "IO::Socket::INET",
these are accepted as synonyms for "LocalHost" and "LocalService" respectively.
LocalAddrInfo => ARRAY
Alternate form of specifying the local address to "bind()" to. This should be an
array of the form returned by "Socket::getaddrinfo".
This parameter takes precedence over the "Local*", "Family", "Type" and "Proto"
arguments.
Family => INT
The address family to pass to "getaddrinfo" (e.g. "AF_INET", "AF_INET6").
Normally this will be left undefined, and "getaddrinfo" will search using any
address family supported by the system.
Type => INT
The socket type to pass to "getaddrinfo" (e.g. "SOCK_STREAM", "SOCK_DGRAM").
Normally defined by the caller; if left undefined "getaddrinfo" may attempt to
infer the type from the service name.
Proto => STRING or INT
The IP protocol to use for the socket (e.g. 'tcp', "IPPROTO_TCP",
'udp',"IPPROTO_UDP"). Normally this will be left undefined, and either
"getaddrinfo" or the kernel will choose an appropriate value. May be given either
in string name or numeric form.
GetAddrInfoFlags => INT
More flags to pass to the "getaddrinfo()" function. If not supplied, a default of
"AI_ADDRCONFIG" will be used.
These flags will be combined with "AI_PASSIVE" if the "Listen" argument is given.
For more information see the documentation about "getaddrinfo()" in the Socket
module.
Listen => INT
If defined, puts the socket into listening mode where new connections can be
accepted using the "accept" method. The value given is used as the listen(2) queue
size.
ReuseAddr => BOOL
If true, set the "SO_REUSEADDR" sockopt
ReusePort => BOOL
If true, set the "SO_REUSEPORT" sockopt (not all OSes implement this sockopt)
Broadcast => BOOL
If true, set the "SO_BROADCAST" sockopt
Sockopts => ARRAY
An optional array of other socket options to apply after the three listed above.
The value is an ARRAY containing 2- or 3-element ARRAYrefs. Each inner array
relates to a single option, giving the level and option name, and an optional
value. If the value element is missing, it will be given the value of a platform-
sized integer 1 constant (i.e. suitable to enable most of the common boolean
options).
For example, both options given below are equivalent to setting "ReuseAddr".
Sockopts => [
[ SOL_SOCKET, SO_REUSEADDR ],
[ SOL_SOCKET, SO_REUSEADDR, pack( "i", 1 ) ],
]
V6Only => BOOL
If defined, set the "IPV6_V6ONLY" sockopt when creating "PF_INET6" sockets to the
given value. If true, a listening-mode socket will only listen on the "AF_INET6"
addresses; if false it will also accept connections from "AF_INET" addresses.
If not defined, the socket option will not be changed, and default value set by
the operating system will apply. For repeatable behaviour across platforms it is
recommended this value always be defined for listening-mode sockets.
Note that not all platforms support disabling this option. Some, at least OpenBSD
and MirBSD, will fail with "EINVAL" if you attempt to disable it. To determine
whether it is possible to disable, you may use the class method
if( IO::Socket::IP->CAN_DISABLE_V6ONLY ) {
...
}
else {
...
}
If your platform does not support disabling this option but you still want to
listen for both "AF_INET" and "AF_INET6" connections you will have to create two
listening sockets, one bound to each protocol.
MultiHomed
This "IO::Socket::INET"-style argument is ignored, except if it is defined but
false. See the "IO::Socket::INET" INCOMPATIBILITES section below.
However, the behaviour it enables is always performed by "IO::Socket::IP".
Blocking => BOOL
If defined but false, the socket will be set to non-blocking mode. Otherwise it
will default to blocking mode. See the NON-BLOCKING section below for more detail.
Timeout => NUM
If defined, gives a maximum time in seconds to block per "connect()" call when in
blocking mode. If missing, no timeout is applied other than that provided by the
underlying operating system. When in non-blocking mode this parameter is ignored.
Note that if the hostname resolves to multiple address candidates, the same
timeout will apply to each connection attempt individually, rather than to the
operation as a whole. Further note that the timeout does not apply to the initial
hostname resolve operation, if connecting by hostname.
This behviour is copied inspired by "IO::Socket::INET"; for more fine grained
control over connection timeouts, consider performing a nonblocking connect
directly.
If neither "Type" nor "Proto" hints are provided, a default of "SOCK_STREAM" and
"IPPROTO_TCP" respectively will be set, to maintain compatibility with "IO::Socket::INET".
Other named arguments that are not recognised are ignored.
If neither "Family" nor any hosts or addresses are passed, nor any *AddrInfo, then the
constructor has no information on which to decide a socket family to create. In this case,
it performs a "getaddinfo" call with the "AI_ADDRCONFIG" flag, no host name, and a service
name of "0", and uses the family of the first returned result.
If the constructor fails, it will set $@ to an appropriate error message; this may be from
$! or it may be some other string; not every failure necessarily has an associated "errno"
value.
new (one arg)
$sock = IO::Socket::IP->new( $peeraddr )
As a special case, if the constructor is passed a single argument (as opposed to an even-
sized list of key/value pairs), it is taken to be the value of the "PeerAddr" parameter.
This is parsed in the same way, according to the behaviour given in the "PeerHost" AND
"LocalHost" PARSING section below.
METHODS
As well as the following methods, this class inherits all the methods in IO::Socket and
IO::Handle.
sockhost_service
( $host, $service ) = $sock->sockhost_service( $numeric )
Returns the hostname and service name of the local address (that is, the socket address
given by the "sockname" method).
If $numeric is true, these will be given in numeric form rather than being resolved into
names.
The following four convenience wrappers may be used to obtain one of the two values
returned here. If both host and service names are required, this method is preferable to
the following wrappers, because it will call getnameinfo(3) only once.
sockhost
$addr = $sock->sockhost
Return the numeric form of the local address as a textual representation
sockport
$port = $sock->sockport
Return the numeric form of the local port number
sockhostname
$host = $sock->sockhostname
Return the resolved name of the local address
sockservice
$service = $sock->sockservice
Return the resolved name of the local port number
sockaddr
$addr = $sock->sockaddr
Return the local address as a binary octet string
peerhost_service
( $host, $service ) = $sock->peerhost_service( $numeric )
Returns the hostname and service name of the peer address (that is, the socket address
given by the "peername" method), similar to the "sockhost_service" method.
The following four convenience wrappers may be used to obtain one of the two values
returned here. If both host and service names are required, this method is preferable to
the following wrappers, because it will call getnameinfo(3) only once.
peerhost
$addr = $sock->peerhost
Return the numeric form of the peer address as a textual representation
peerport
$port = $sock->peerport
Return the numeric form of the peer port number
peerhostname
$host = $sock->peerhostname
Return the resolved name of the peer address
peerservice
$service = $sock->peerservice
Return the resolved name of the peer port number
peeraddr
$addr = $peer->peeraddr
Return the peer address as a binary octet string
as_inet
$inet = $sock->as_inet
Returns a new IO::Socket::INET instance wrapping the same filehandle. This may be useful
in cases where it is required, for backward-compatibility, to have a real object of
"IO::Socket::INET" type instead of "IO::Socket::IP". The new object will wrap the same
underlying socket filehandle as the original, so care should be taken not to continue to
use both objects concurrently. Ideally the original $sock should be discarded after this
method is called.
This method checks that the socket domain is "PF_INET" and will throw an exception if it
isn't.
NON-BLOCKING
If the constructor is passed a defined but false value for the "Blocking" argument then
the socket is put into non-blocking mode. When in non-blocking mode, the socket will not
be set up by the time the constructor returns, because the underlying connect(2) syscall
would otherwise have to block.
The non-blocking behaviour is an extension of the "IO::Socket::INET" API, unique to
"IO::Socket::IP", because the former does not support multi-homed non-blocking connect.
When using non-blocking mode, the caller must repeatedly check for writeability on the
filehandle (for instance using "select" or "IO::Poll"). Each time the filehandle is ready
to write, the "connect" method must be called, with no arguments. Note that some operating
systems, most notably "MSWin32" do not report a "connect()" failure using write-ready; so
you must also "select()" for exceptional status.
While "connect" returns false, the value of $! indicates whether it should be tried again
(by being set to the value "EINPROGRESS", or "EWOULDBLOCK" on MSWin32), or whether a
permanent error has occurred (e.g. "ECONNREFUSED").
Once the socket has been connected to the peer, "connect" will return true and the socket
will now be ready to use.
Note that calls to the platform's underlying getaddrinfo(3) function may block. If
"IO::Socket::IP" has to perform this lookup, the constructor will block even when in non-
blocking mode.
To avoid this blocking behaviour, the caller should pass in the result of such a lookup
using the "PeerAddrInfo" or "LocalAddrInfo" arguments. This can be achieved by using
Net::LibAsyncNS, or the getaddrinfo(3) function can be called in a child process.
use IO::Socket::IP;
use Errno qw( EINPROGRESS EWOULDBLOCK );
my @peeraddrinfo = ... # Caller must obtain the getaddinfo result here
my $socket = IO::Socket::IP->new(
PeerAddrInfo => \@peeraddrinfo,
Blocking => 0,
) or die "Cannot construct socket - $@";
while( !$socket->connect and ( $! == EINPROGRESS || $! == EWOULDBLOCK ) ) {
my $wvec = '';
vec( $wvec, fileno $socket, 1 ) = 1;
my $evec = '';
vec( $evec, fileno $socket, 1 ) = 1;
select( undef, $wvec, $evec, undef ) or die "Cannot select - $!";
}
die "Cannot connect - $!" if $!;
...
The example above uses "select()", but any similar mechanism should work analogously.
"IO::Socket::IP" takes care when creating new socket filehandles to preserve the actual
file descriptor number, so such techniques as "poll" or "epoll" should be transparent to
its reallocation of a different socket underneath, perhaps in order to switch protocol
family between "PF_INET" and "PF_INET6".
For another example using "IO::Poll" and "Net::LibAsyncNS", see the
examples/nonblocking_libasyncns.pl file in the module distribution.
"PeerHost" AND "LocalHost" PARSING
To support the "IO::Socket::INET" API, the host and port information may be passed in a
single string rather than as two separate arguments.
If either "LocalHost" or "PeerHost" (or their "...Addr" synonyms) have any of the
following special forms then special parsing is applied.
The value of the "...Host" argument will be split to give both the hostname and port (or
service name):
hostname.example.org:http # Host name
192.0.2.1:80 # IPv4 address
[2001:db8::1]:80 # IPv6 address
In each case, the port or service name (e.g. 80) is passed as the "LocalService" or
"PeerService" argument.
Either of "LocalService" or "PeerService" (or their "...Port" synonyms) can be either a
service name, a decimal number, or a string containing both a service name and number, in
a form such as
http(80)
In this case, the name ("http") will be tried first, but if the resolver does not
understand it then the port number (80) will be used instead.
If the "...Host" argument is in this special form and the corresponding "...Service" or
"...Port" argument is also defined, the one parsed from the "...Host" argument will take
precedence and the other will be ignored.
split_addr
( $host, $port ) = IO::Socket::IP->split_addr( $addr )
Utility method that provides the parsing functionality described above. Returns a
2-element list, containing either the split hostname and port description if it could be
parsed, or the given address and "undef" if it was not recognised.
IO::Socket::IP->split_addr( "hostname:http" )
# ( "hostname", "http" )
IO::Socket::IP->split_addr( "192.0.2.1:80" )
# ( "192.0.2.1", "80" )
IO::Socket::IP->split_addr( "[2001:db8::1]:80" )
# ( "2001:db8::1", "80" )
IO::Socket::IP->split_addr( "something.else" )
# ( "something.else", undef )
join_addr
$addr = IO::Socket::IP->join_addr( $host, $port )
Utility method that performs the reverse of "split_addr", returning a string formed by
joining the specified host address and port number. The host address will be wrapped in
"[]" brackets if required (because it is a raw IPv6 numeric address).
This can be especially useful when combined with the "sockhost_service" or
"peerhost_service" methods.
say "Connected to ", IO::Socket::IP->join_addr( $sock->peerhost_service );
"IO::Socket::INET" INCOMPATIBILITES
• The behaviour enabled by "MultiHomed" is in fact implemented by "IO::Socket::IP" as it
is required to correctly support searching for a useable address from the results of
the getaddrinfo(3) call. The constructor will ignore the value of this argument,
except if it is defined but false. An exception is thrown in this case, because that
would request it disable the getaddrinfo(3) search behaviour in the first place.
• "IO::Socket::IP" implements both the "Blocking" and "Timeout" parameters, but it
implements the interaction of both in a different way.
In "::INET", supplying a timeout overrides the non-blocking behaviour, meaning that
the "connect()" operation will still block despite that the caller asked for a non-
blocking socket. This is not explicitly specified in its documentation, nor does this
author believe that is a useful behaviour - it appears to come from a quirk of
implementation.
In "::IP" therefore, the "Blocking" parameter takes precedence - if a non-blocking
socket is requested, no operation will block. The "Timeout" parameter here simply
defines the maximum time that a blocking "connect()" call will wait, if it blocks at
all.
In order to specifically obtain the "blocking connect then non-blocking send and
receive" behaviour of specifying this combination of options to "::INET" when using
"::IP", perform first a blocking connect, then afterwards turn the socket into
nonblocking mode.
my $sock = IO::Socket::IP->new(
PeerHost => $peer,
Timeout => 20,
) or die "Cannot connect - $@";
$sock->blocking( 0 );
This code will behave identically under both "IO::Socket::INET" and "IO::Socket::IP".
TODO
• Investigate whether "POSIX::dup2" upsets BSD's "kqueue" watchers, and if so, consider
what possible workarounds might be applied.
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>