phpman > perldoc > IO::Multiplex(3pm)

NAME
    IO::Multiplex - Manage IO on many file handles

SYNOPSIS
      use IO::Multiplex;

      my $mux = new IO::Multiplex;
      $mux->add($fh1);
      $mux->add(\*FH2);
      $mux->set_callback_object(...);
      $mux->listen($server_socket);
      $mux->loop;

      sub mux_input { ... }

    "IO::Multiplex" is designed to take the effort out of managing multiple file handles. It is
    essentially a really fancy front end to the "select" system call. In addition to maintaining the
    "select" loop, it buffers all input and output to/from the file handles. It can also accept
    incoming connections on one or more listen sockets.

DESCRIPTION
    It is object oriented in design, and will notify you of significant events by calling methods on
    an object that you supply. If you are not using objects, you can simply supply "__PACKAGE__"
    instead of an object reference.

    You may have one callback object registered for each file handle, or one global one. Possibly
    both -- the per-file handle callback object will be used instead of the global one.

    Each file handle may also have a timer associated with it. A callback function is called when
    the timer expires.

  Handling input on descriptors
    When input arrives on a file handle, the "mux_input" method is called on the appropriate
    callback object. This method is passed three arguments (in addition to the object reference
    itself of course):

    1   a reference to the mux,

    2   A reference to the file handle, and

    3   a reference to the input buffer for the file handle.

    The method should remove the data that it has consumed from the reference supplied. It may leave
    unconsumed data in the input buffer.

  Handling output to descriptors
    If "IO::Multiplex" did not handle output to the file handles as well as input from them, then
    there is a chance that the program could block while attempting to write. If you let the
    multiplexer buffer the output, it will write the data only when the file handle is capable of
    receiveing it.

    The basic method for handing output to the multiplexer is the "write" method, which simply takes
    a file descriptor and the data to be written, like this:

        $mux->write($fh, "Some data");

    For convenience, when the file handle is "add"ed to the multiplexer, it is tied to a special
    class which intercepts all attempts to write to the file handle. Thus, you can use print and
    printf to send output to the handle in a normal manner:

        printf $fh "%s%d%X", $foo, $bar, $baz

    Unfortunately, Perl support for tied file handles is incomplete, and functions such as "send"
    cannot be supported.

    Also, file handle object methods such as the "send" method of "IO::Socket" cannot be
    intercepted.

EXAMPLES
  Simple Example
    This is a simple telnet-like program, which demonstrates the concepts covered so far. It does
    not really work too well against a telnet server, but it does OK against the sample server
    presented further down.

        use IO::Socket;
        use IO::Multiplex;

        # Create a multiplex object
        my $mux  = new IO::Multiplex;
        # Connect to the host/port specified on the command line,
        # or localhost:23
        my $sock = new IO::Socket::INET(Proto    => 'tcp',
                                        PeerAddr => shift || 'localhost',
                                        PeerPort => shift || 23)
            or die "socket: $@";

        # add the relevant file handles to the mux
        $mux->add($sock);
        $mux->add(\*STDIN);
        # We want to buffer output to the terminal.  This prevents the program
        # from blocking if the user hits CTRL-S for example.
        $mux->add(\*STDOUT);

        # We're not object oriented, so just request callbacks to the
        # current package
        $mux->set_callback_object(__PACKAGE__);

        # Enter the main mux loop.
        $mux->loop;

        # mux_input is called when input is available on one of
        # the descriptors.
        sub mux_input {
            my $package = shift;
            my $mux     = shift;
            my $fh      = shift;
            my $input   = shift;

            # Figure out whence the input came, and send it on to the
            # other place.
            if ($fh == $sock) {
                print STDOUT $$input;
            } else {
                print $sock $$input;
            }
            # Remove the input from the input buffer.
            $$input = '';
        }

        # This gets called if the other end closes the connection.
        sub mux_close {
            print STDERR "Connection Closed\n";
            exit;
        }

  A server example
    Servers are just as simple to write. We just register a listen socket with the multiplex object
    "listen" method. It will automatically accept connections on it and add them to its list of
    active file handles.

    This example is a simple chat server.

        use IO::Socket;
        use IO::Multiplex;

        my $mux  = new IO::Multiplex;

        # Create a listening socket
        my $sock = new IO::Socket::INET(Proto     => 'tcp',
                                        LocalPort => shift || 2300,
                                        Listen    => 4)
            or die "socket: $@";

        # We use the listen method instead of the add method.
        $mux->listen($sock);

        $mux->set_callback_object(__PACKAGE__);
        $mux->loop;

        sub mux_input {
            my $package = shift;
            my $mux     = shift;
            my $fh      = shift;
            my $input   = shift;

            # The handles method returns a list of references to handles which
            # we have registered, except for listen sockets.
            foreach $c ($mux->handles) {
                print $c $$input;
            }
            $$input = '';
        }

  A more complex server example
    Let us take a look at the beginnings of a multi-user game server. We will have a Player object
    for each player.

        # Paste the above example in here, up to but not including the
        # mux_input subroutine.

        # mux_connection is called when a new connection is accepted.
        sub mux_connection {
            my $package = shift;
            my $mux     = shift;
            my $fh      = shift;

            # Construct a new player object
            Player->new($mux, $fh);
        }

        package Player;

        my %players = ();

        sub new {
            my $package = shift;
            my $self    = bless { mux  => shift,
                                  fh   => shift } => $package;

            # Register the new player object as the callback specifically for
            # this file handle.

            $self->{mux}->set_callback_object($self, $self->{fh});
            print $self->{fh}
                "Greetings, Professor.  Would you like to play a game?\n";

            # Register this player object in the main list of players
            $players{$self} = $self;
            $mux->set_timeout($self->{fh}, 1);
        }

        sub players { return values %players; }

        sub mux_input {
            my $self = shift;
            shift; shift;         # These two args are boring
            my $input = shift;    # Scalar reference to the input

            # Process each line in the input, leaving partial lines
            # in the input buffer
            while ($$input =~ s/^(.*?)\n//) {
                $self->process_command($1);
            }
        }

        sub mux_close {
           my $self = shift;

           # Player disconnected;
           # [Notify other players or something...]
           delete $players{$self};
        }
        # This gets called every second to update player info, etc...
        sub mux_timeout {
            my $self = shift;
            my $mux  = shift;

            $self->heartbeat;
            $mux->set_timeout($self->{fh}, 1);
        }

METHODS
  new
    Construct a new "IO::Multiplex" object.

        $mux = new IO::Multiplex;

  listen
    Add a socket to be listened on. The socket should have had the "bind" and "listen" system calls
    already applied to it. The "IO::Socket" module will do this for you.

        $socket = new IO::Socket::INET(Listen => ..., LocalAddr => ...);
        $mux->listen($socket);

    Connections will be automatically accepted and "add"ed to the multiplex object. "The
    mux_connection" callback method will also be called.

  add
    Add a file handle to the multiplexer.

        $mux->add($fh);

    As a side effect, this sets non-blocking mode on the handle, and disables STDIO buffering. It
    also ties it to intercept output to the handle.

  remove
    Removes a file handle from the multiplexer. This also unties the handle. It does not currently
    turn STDIO buffering back on, or turn off non-blocking mode.

        $mux->remove($fh);

  set_callback_object
    Set the object on which callbacks are made. If you are not using objects, you can specify the
    name of the package into which the method calls are to be made.

    If a file handle is supplied, the callback object is specific for that handle:

        $mux->set_callback_object($object, $fh);

    Otherwise, it is considered a default callback object, and is used when events occur on a file
    handle that does not have its own callback object.

        $mux->set_callback_object(__PACKAGE__);

    The previously registered object (if any) is returned.

    See also the CALLBACK INTERFACE section.

  kill_output
    Remove any pending output on a file descriptor.

        $mux->kill_output($fh);

  outbuffer
    Return or set the output buffer for a descriptor

        $output = $mux->outbuffer($fh);
        $mux->outbuffer($fh, $output);

  inbuffer
    Return or set the input buffer for a descriptor

        $input = $mux->inbuffer($fh);
        $mux->inbuffer($fh, $input);

  set_timeout
    Set the timer for a file handle. The timeout value is a certain number of seconds in the future,
    after which the "mux_timeout" callback is called.

    If the "Time::HiRes" module is installed, the timers may be specified in fractions of a second.

    Timers are not reset automatically.

        $mux->set_timeout($fh, 23.6);

    Use "$mux->set_timeout($fh, undef)" to cancel a timer.

  handles
    Returns a list of handles that the "IO::Multiplex" object knows about, excluding listen sockets.

        @handles = $mux->handles;

  loop
    Enter the main loop and start processing IO events.

        $mux->loop;

  endloop
    Prematurly terminate the loop. The loop will automatically terminate when there are no remaining
    descriptors to be watched.

        $mux->endloop;

  udp_peer
    Get peer endpoint of where the last udp packet originated.

        $saddr = $mux->udp_peer($fh);

  is_udp
    Sometimes UDP packets require special attention. This method will tell if a file handle is of
    type UDP.

        $is_udp = $mux->is_udp($fh);

  write
    Send output to a file handle.

        $mux->write($fh, "'ere I am, JH!\n");

  shutdown
    Shut down a socket for reading or writing or both. See the "shutdown" Perl documentation for
    further details.

    If the shutdown is for reading, it happens immediately. However, shutdowns for writing are
    delayed until any pending output has been successfully written to the socket.

        $mux->shutdown($socket, 1);

  close
    Close a handle. Always use this method to close a handle that is being watched by the
    multiplexer.

        $mux->close($fh);

CALLBACK INTERFACE
    Callback objects should support the following interface. You do not have to provide all of these
    methods, just provide the ones you are interested in.

    All methods receive a reference to the callback object (or package) as their first argument, in
    the traditional object oriented way. References to the "IO::Multiplex" object and the relevant
    file handle are also provided. This will be assumed in the method descriptions.

  mux_input
    Called when input is ready on a descriptor. It is passed a reference to the input buffer. It
    should remove any input that it has consumed, and leave any partially received data in the
    buffer.

        sub mux_input {
            my $self = shift;
            my $mux  = shift;
            my $fh   = shift;
            my $data = shift;

            # Process each line in the input, leaving partial lines
            # in the input buffer
            while ($$data =~ s/^(.*?\n)//) {
                $self->process_command($1);
            }
        }

  mux_eof
    This is called when an end-of-file condition is present on the descriptor. This is does not
    nessecarily mean that the descriptor has been closed, as the other end of a socket could have
    used "shutdown" to close just half of the socket, leaving us free to write data back down the
    still open half. Like mux_input, it is also passed a reference to the input buffer. It should
    consume the entire buffer or else it will just be lost.

    In this example, we send a final reply to the other end of the socket, and then shut it down for
    writing. Since it is also shut down for reading (implicly by the EOF condition), it will be
    closed once the output has been sent, after which the mux_close callback will be called.

        sub mux_eof {
            my $self = shift;
            my $mux  = shift;
            my $fh   = shift;

            print $fh "Well, goodbye then!\n";
            $mux->shutdown($fh, 1);
        }

  mux_close
    Called when a handle has been completely closed. At the time that "mux_close" is called, the
    handle will have been removed from the multiplexer, and untied.

  mux_outbuffer_empty
    Called after all pending output has been written to the file descriptor.

  mux_connection
    Called upon a new connection being accepted on a listen socket.

  mux_timeout
    Called when a timer expires.

AUTHOR
    Copyright 1999 Bruce J Keeler <bruce AT gridpoint.com>

    Copyright 2001-2008 Rob Brown <bbb AT cpan.org>

    Released under the same terms as Perl itself.

    $Id: Multiplex.pm,v 1.45 2015/04/09 21:27:54 rob Exp $