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]\n"; },
    on_listen_error  => sub { print STDERR "Cannot listen\n"; },
 );

 $loop->loop_forever;

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]\n"; },
    on_listen_error  => sub { print STDERR "Cannot listen\n"; },
 );

 $loop->loop_forever;

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). 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::Loop'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.

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 - $!\n";

 $listener->listen(
    handle => $socket,
 );

 $loop->loop_forever;

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::Loop 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>

cpanm IO::Async

perl -MCPAN -e shell
install IO::Async