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IO::Async::Listener.3pm

NAME

"IO::Async::Listener" - listen on network sockets for incoming connections

SYNOPSIS

  use IO::Async::Listener;
  use IO::Async::Stream;
 
  use IO::Async::Loop;
  my $loop = IO::Async::Loop->new();
 
  my $listener = IO::Async::Listener->new(
     on_accept => sub {
        my ( $newclient ) = @_;
 
        $loop->add( IO::Async::Stream->new(
           handle => $newclient,
 
           on_read => sub {
              my ( $self, $buffref, $closed ) = @_;
              $self->write( $$buffref );
              $$buffref = "";
              return 0;
           },
        ) );
     },
  );
 
  $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_accept => 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.

This object may be used in one of two ways; with a callback function, or as a base class.

Callbacks

If the "on_accept" key is supplied to the constructor, it should contain a CODE reference to a callback function to be invoked when a new client connects to the socket. It is passed an "IO::Socket" reference to the newly accepted socket:

  $on_accept->( $self, $clientsocket )
 
 

Base Class

If a subclass is built, then it can override the "on_accept" method.

  $self->on_accept( $clientsocket )
 
 

PARAMETERS

The following named parameters may be passed to "new" or "configure":

on_accept => CODE

A callback that is invoked whenever a new client connects to the socket. If not supplied the subclass method will be called instead.

handle => IO

The IO handle containing an existing listen-mode socket.

METHODS

$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.

The address (or each element of the "addrs" array) should be a reference to an array, with at least the following elements:

  [ $family, $socktype, $protocol, $address ]
 
 

The first three arguments will be passed to a "socket()" call and, if successful, the fourth to a "bind()" call on the resulting socket. The socket will then be "listen()"ed to put it into listening mode. Any trailing elements in this array will be ignored.

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.

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. Becasue there is no one error message that stands out as particularly noteworthy, none is given to this continuation. To track individual errors, see the "on_fail" callback.

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()" 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.

AUTHOR

Paul Evans <leonerd@leonerd.org.uk>