IO::Async::Listener(3pm) User Contributed Perl Documentation IO::Async::Listener(3pm)
NAME
"IO::Async::Listener" - listen on network sockets for incoming connections
SYNOPSIS
use IO::Async::Listener;
use IO::Async::Loop;
my $loop = IO::Async::Loop->new;
my $listener = IO::Async::Listener->new(
on_stream => sub {
my ( undef, $stream ) = @_;
$stream->configure(
on_read => sub {
my ( $self, $buffref, $eof ) = @_;
$self->write( $$buffref );
$$buffref = "";
return 0;
},
);
$loop->add( $stream );
},
);
$loop->add( $listener );
$listener->listen(
service => "echo",
socktype => 'stream',
on_resolve_error => sub { print STDERR "Cannot resolve - $_[0]
"; },
on_listen_error => sub { print STDERR "Cannot listen
"; },
);
$loop->run;
This object can also be used indirectly via an "IO::Async::Loop":
use IO::Async::Stream;
use IO::Async::Loop;
my $loop = IO::Async::Loop->new;
$loop->listen(
service => "echo",
socktype => 'stream',
on_stream => sub {
...
},
on_resolve_error => sub { print STDERR "Cannot resolve - $_[0]
"; },
on_listen_error => sub { print STDERR "Cannot listen
"; },
);
$loop->run;
DESCRIPTION
This subclass of IO::Async::Handle adds behaviour which watches a socket in listening mode, to accept incoming connections on them.
A Listener can be constructed and given a existing socket in listening mode. Alternatively, the Listener can construct a socket by calling
the "listen" method. Either a list of addresses can be provided, or a service name can be looked up using the underlying loop's "resolve"
method.
EVENTS
The following events are invoked, either using subclass methods or CODE references in parameters:
on_accept $clientsocket
Invoked whenever a new client connects to the socket.
on_stream $stream
An alternative to "on_accept", this an instance of IO::Async::Stream when a new client connects. This is provided as a convenience for the
common case that a Stream object is required as the transport for a Protocol object.
on_socket $socket
Similar to "on_stream", but constructs an instance of IO::Async::Socket. This is most useful for "SOCK_DGRAM" or "SOCK_RAW" sockets.
on_accept_error $socket, $errno
Optional. Invoked if the "accept" syscall indicates an error (other than "EAGAIN" or "EWOULDBLOCK"). If not provided, failures of "accept"
will simply be ignored.
PARAMETERS
The following named parameters may be passed to "new" or "configure":
on_accept => CODE
on_stream => CODE
on_socket => CODE
CODE reference for the event handlers. Because of the mutually-exclusive nature of their behaviour, only one of these may be set at
a time. Setting one will remove the other two.
handle => IO
The IO handle containing an existing listen-mode socket.
METHODS
$name = $listener->sockname
Returns the "sockname" of the underlying listening socket
$family = $listener->family
Returns the socket address family of the underlying listening socket
$socktype = $listener->socktype
Returns the socket type of the underlying listening socket
$listener->listen( %params )
This method sets up a listening socket using the addresses given, and will invoke the "on_accept" callback each time a new connection is
accepted on the socket. Addresses may be given directly, or they may be looked up using the system's name resolver.
If multiple addresses are given, or resolved from the service and hostname, then each will be attempted in turn until one succeeds.
In plain address mode, the %params hash takes the following keys:
addrs => ARRAY
Reference to an array of (possibly-multiple) address structures to attempt to listen on. Each should be in the layout described for
"addr". Such a layout is returned by the "getaddrinfo" named resolver.
addr => ARRAY
Shortcut for passing a single address to listen on; it may be passed directly with this key, instead of in another array of its
own. This should be in a format recognised by IO::Async::OS's "extract_addrinfo" method. See also the "EXAMPLES" section.
In named resolver mode, the %params hash takes the following keys:
service => STRING
The service name to listen on.
host => STRING
The hostname to listen on. Optional. Will listen on all addresses if not supplied.
family => INT
socktype => INT
protocol => INT
flags => INT
Optional. Other arguments to pass along with "host" and "service" to the "getaddrinfo" call.
socktype => STRING
Optionally may instead be one of the values 'stream', 'dgram' or 'raw' to stand for "SOCK_STREAM", "SOCK_DGRAM" or "SOCK_RAW". This
utility is provided to allow the caller to avoid a separate "use Socket" only for importing these constants.
on_resolve_error => CODE
A continuation that is invoked when the name resolution attempt fails. This is invoked in the same way as the "on_error"
continuation for the "resolve" method.
It is necessary to pass the "socktype" hint to the resolver when resolving the host/service names into an address, as some OS's
"getaddrinfo" functions require this hint. A warning is emitted if neither "socktype" nor "protocol" hint is defined when performing a
"getaddrinfo" lookup. To avoid this warning while still specifying no particular "socktype" hint (perhaps to invoke some OS-specific
behaviour), pass 0 as the "socktype" value.
In either case, the following keys are also taken:
on_listen => CODE
Optional. A callback that is invoked when the listening socket is ready.
$on_listen->( $listener )
on_listen_error => CODE
A continuation this is invoked after all of the addresses have been tried, and none of them succeeded. It will be passed the most
significant error that occurred, and the name of the operation it occurred in. Errors from the listen(2) syscall are considered
most significant, then bind(2), then sockopt(2), then finally socket(2).
on_fail => CODE
Optional. A callback that is invoked if a syscall fails while attempting to create a listening sockets. It is passed the name of
the syscall that failed, the arguments that were passed to it, and the error generated. I.e.
$on_fail->( "socket", $family, $socktype, $protocol, $! );
$on_fail->( "sockopt", $sock, $optname, $optval, $! );
$on_fail->( "bind", $sock, $address, $! );
$on_fail->( "listen", $sock, $queuesize, $! );
queuesize => INT
Optional. The queue size to pass to the listen(2) calls. If not supplied, then 3 will be given instead.
reuseaddr => BOOL
Optional. If true or not supplied then the "SO_REUSEADDR" socket option will be set. To prevent this, pass a false value such as 0.
v6only => BOOL
Optional. If defined, sets or clears the "IPV6_V6ONLY" socket option on "PF_INET6" sockets. This option disables the ability of
"PF_INET6" socket to accept connections from "AF_INET" addresses. Not all operating systems allow this option to be disabled.
As a convenience, it also supports a "handle" argument, which is passed directly to "configure".
EXAMPLES
Listening on UNIX Sockets
The "handle" argument can be passed an existing socket already in listening mode, making it possible to listen on other types of socket
such as UNIX sockets.
use IO::Async::Listener;
use IO::Socket::UNIX;
use IO::Async::Loop;
my $loop = IO::Async::Loop->new;
my $listener = IO::Async::Listener->new(
on_stream => sub {
my ( undef, $stream ) = @_;
$stream->configure(
on_read => sub {
my ( $self, $buffref, $eof ) = @_;
$self->write( $$buffref );
$$buffref = "";
return 0;
},
);
$loop->add( $stream );
},
);
$loop->add( $listener );
my $socket = IO::Socket::UNIX->new(
Local => "echo.sock",
Listen => 1,
) or die "Cannot make UNIX socket - $!
";
$listener->listen(
handle => $socket,
);
$loop->run;
Passing Plain Socket Addresses
The "addr" or "addrs" parameters should contain a definition of a plain socket address in a form that the IO::Async::OS "extract_addrinfo"
method can use.
This example shows how to use the "Socket" functions to construct one for TCP port 8001 on address 10.0.0.1:
$listener->listen(
addr => {
family => "inet",
socktype => "stream",
port => 8001,
ip => "10.0.0.1",
},
...
);
This example shows another way to listen on a UNIX socket, similar to the earlier example:
$listener->listen(
addr => {
family => "unix",
socktype => "stream",
path => "echo.sock",
},
...
);
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
perl v5.14.2 2012-10-24 IO::Async::Listener(3pm)