Provided by: perl-doc_5.40.1-2ubuntu0.1_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 - $IO::Socket::errstr";
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 - $IO::Socket::errstr\n";
print "Created a socket of type " . ref($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 behaviour 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 $IO::Socket::errstr and $@ 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>
perl v5.40.1 2025-04-14 IO::Socket::IP(3perl)