1IO::Multiplex(3)      User Contributed Perl Documentation     IO::Multiplex(3)
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3
4

NAME

6       IO::Multiplex - Manage IO on many file handles
7

SYNOPSIS

9         use IO::Multiplex;
10
11         my $mux = new IO::Multiplex;
12         $mux->add($fh1);
13         $mux->add(\*FH2);
14         $mux->set_callback_object(...);
15         $mux->listen($server_socket);
16         $mux->loop;
17
18         sub mux_input { ... }
19
20       "IO::Multiplex" is designed to take the effort out of managing multiple
21       file handles. It is essentially a really fancy front end to the
22       "select" system call. In addition to maintaining the "select" loop, it
23       buffers all input and output to/from the file handles.  It can also
24       accept incoming connections on one or more listen sockets.
25

DESCRIPTION

27       It is object oriented in design, and will notify you of significant
28       events by calling methods on an object that you supply.  If you are not
29       using objects, you can simply supply "__PACKAGE__" instead of an object
30       reference.
31
32       You may have one callback object registered for each file handle, or
33       one global one.  Possibly both -- the per-file handle callback object
34       will be used instead of the global one.
35
36       Each file handle may also have a timer associated with it.  A callback
37       function is called when the timer expires.
38
39   Handling input on descriptors
40       When input arrives on a file handle, the "mux_input" method is called
41       on the appropriate callback object.  This method is passed three
42       arguments (in addition to the object reference itself of course):
43
44       1.  a reference to the mux,
45
46       2.  A reference to the file handle, and
47
48       3.  a reference to the input buffer for the file handle.
49
50       The method should remove the data that it has consumed from the
51       reference supplied.  It may leave unconsumed data in the input buffer.
52
53   Handling output to descriptors
54       If "IO::Multiplex" did not handle output to the file handles as well as
55       input from them, then there is a chance that the program could block
56       while attempting to write.  If you let the multiplexer buffer the
57       output, it will write the data only when the file handle is capable of
58       receiveing it.
59
60       The basic method for handing output to the multiplexer is the "write"
61       method, which simply takes a file descriptor and the data to be
62       written, like this:
63
64           $mux->write($fh, "Some data");
65
66       For convenience, when the file handle is "add"ed to the multiplexer, it
67       is tied to a special class which intercepts all attempts to write to
68       the file handle.  Thus, you can use print and printf to send output to
69       the handle in a normal manner:
70
71           printf $fh "%s%d%X", $foo, $bar, $baz
72
73       Unfortunately, Perl support for tied file handles is incomplete, and
74       functions such as "send" cannot be supported.
75
76       Also, file handle object methods such as the "send" method of
77       "IO::Socket" cannot be intercepted.
78

EXAMPLES

80   Simple Example
81       This is a simple telnet-like program, which demonstrates the concepts
82       covered so far.  It does not really work too well against a telnet
83       server, but it does OK against the sample server presented further
84       down.
85
86           use IO::Socket;
87           use IO::Multiplex;
88
89           # Create a multiplex object
90           my $mux  = new IO::Multiplex;
91           # Connect to the host/port specified on the command line,
92           # or localhost:23
93           my $sock = new IO::Socket::INET(Proto    => 'tcp',
94                                           PeerAddr => shift || 'localhost',
95                                           PeerPort => shift || 23)
96               or die "socket: $@";
97
98           # add the relevant file handles to the mux
99           $mux->add($sock);
100           $mux->add(\*STDIN);
101           # We want to buffer output to the terminal.  This prevents the program
102           # from blocking if the user hits CTRL-S for example.
103           $mux->add(\*STDOUT);
104
105           # We're not object oriented, so just request callbacks to the
106           # current package
107           $mux->set_callback_object(__PACKAGE__);
108
109           # Enter the main mux loop.
110           $mux->loop;
111
112           # mux_input is called when input is available on one of
113           # the descriptors.
114           sub mux_input {
115               my $package = shift;
116               my $mux     = shift;
117               my $fh      = shift;
118               my $input   = shift;
119
120               # Figure out whence the input came, and send it on to the
121               # other place.
122               if ($fh == $sock) {
123                   print STDOUT $$input;
124               } else {
125                   print $sock $$input;
126               }
127               # Remove the input from the input buffer.
128               $$input = '';
129           }
130
131           # This gets called if the other end closes the connection.
132           sub mux_close {
133               print STDERR "Connection Closed\n";
134               exit;
135           }
136
137   A server example
138       Servers are just as simple to write.  We just register a listen socket
139       with the multiplex object "listen" method.  It will automatically
140       accept connections on it and add them to its list of active file
141       handles.
142
143       This example is a simple chat server.
144
145           use IO::Socket;
146           use IO::Multiplex;
147
148           my $mux  = new IO::Multiplex;
149
150           # Create a listening socket
151           my $sock = new IO::Socket::INET(Proto     => 'tcp',
152                                           LocalPort => shift || 2300,
153                                           Listen    => 4)
154               or die "socket: $@";
155
156           # We use the listen method instead of the add method.
157           $mux->listen($sock);
158
159           $mux->set_callback_object(__PACKAGE__);
160           $mux->loop;
161
162           sub mux_input {
163               my $package = shift;
164               my $mux     = shift;
165               my $fh      = shift;
166               my $input   = shift;
167
168               # The handles method returns a list of references to handles which
169               # we have registered, except for listen sockets.
170               foreach $c ($mux->handles) {
171                   print $c $$input;
172               }
173               $$input = '';
174           }
175
176   A more complex server example
177       Let us take a look at the beginnings of a multi-user game server.  We
178       will have a Player object for each player.
179
180           # Paste the above example in here, up to but not including the
181           # mux_input subroutine.
182
183           # mux_connection is called when a new connection is accepted.
184           sub mux_connection {
185               my $package = shift;
186               my $mux     = shift;
187               my $fh      = shift;
188
189               # Construct a new player object
190               Player->new($mux, $fh);
191           }
192
193           package Player;
194
195           my %players = ();
196
197           sub new {
198               my $package = shift;
199               my $self    = bless { mux  => shift,
200                                     fh   => shift } => $package;
201
202               # Register the new player object as the callback specifically for
203               # this file handle.
204
205               $self->{mux}->set_callback_object($self, $self->{fh});
206               print $self->{fh}
207                   "Greetings, Professor.  Would you like to play a game?\n";
208
209               # Register this player object in the main list of players
210               $players{$self} = $self;
211               $mux->set_timeout($self->{fh}, 1);
212           }
213
214           sub players { return values %players; }
215
216           sub mux_input {
217               my $self = shift;
218               shift; shift;         # These two args are boring
219               my $input = shift;    # Scalar reference to the input
220
221               # Process each line in the input, leaving partial lines
222               # in the input buffer
223               while ($$input =~ s/^(.*?)\n//) {
224                   $self->process_command($1);
225               }
226           }
227
228           sub mux_close {
229              my $self = shift;
230
231              # Player disconnected;
232              # [Notify other players or something...]
233              delete $players{$self};
234           }
235           # This gets called every second to update player info, etc...
236           sub mux_timeout {
237               my $self = shift;
238               my $mux  = shift;
239
240               $self->heartbeat;
241               $mux->set_timeout($self->{fh}, 1);
242           }
243

METHODS

245   new
246       Construct a new "IO::Multiplex" object.
247
248           $mux = new IO::Multiplex;
249
250   listen
251       Add a socket to be listened on.  The socket should have had the "bind"
252       and "listen" system calls already applied to it.  The "IO::Socket"
253       module will do this for you.
254
255           $socket = new IO::Socket::INET(Listen => ..., LocalAddr => ...);
256           $mux->listen($socket);
257
258       Connections will be automatically accepted and "add"ed to the multiplex
259       object.  "The mux_connection" callback method will also be called.
260
261   add
262       Add a file handle to the multiplexer.
263
264           $mux->add($fh);
265
266       As a side effect, this sets non-blocking mode on the handle, and
267       disables STDIO buffering.  It also ties it to intercept output to the
268       handle.
269
270   remove
271       Removes a file handle from the multiplexer.  This also unties the
272       handle.  It does not currently turn STDIO buffering back on, or turn
273       off non-blocking mode.
274
275           $mux->remove($fh);
276
277   set_callback_object
278       Set the object on which callbacks are made.  If you are not using
279       objects, you can specify the name of the package into which the method
280       calls are to be made.
281
282       If a file handle is supplied, the callback object is specific for that
283       handle:
284
285           $mux->set_callback_object($object, $fh);
286
287       Otherwise, it is considered a default callback object, and is used when
288       events occur on a file handle that does not have its own callback
289       object.
290
291           $mux->set_callback_object(__PACKAGE__);
292
293       The previously registered object (if any) is returned.
294
295       See also the CALLBACK INTERFACE section.
296
297   kill_output
298       Remove any pending output on a file descriptor.
299
300           $mux->kill_output($fh);
301
302   outbuffer
303       Return or set the output buffer for a descriptor
304
305           $output = $mux->outbuffer($fh);
306           $mux->outbuffer($fh, $output);
307
308   inbuffer
309       Return or set the input buffer for a descriptor
310
311           $input = $mux->inbuffer($fh);
312           $mux->inbuffer($fh, $input);
313
314   set_timeout
315       Set the timer for a file handle.  The timeout value is a certain number
316       of seconds in the future, after which the "mux_timeout" callback is
317       called.
318
319       If the "Time::HiRes" module is installed, the timers may be specified
320       in fractions of a second.
321
322       Timers are not reset automatically.
323
324           $mux->set_timeout($fh, 23.6);
325
326       Use "$mux->set_timeout($fh, undef)" to cancel a timer.
327
328   handles
329       Returns a list of handles that the "IO::Multiplex" object knows about,
330       excluding listen sockets.
331
332           @handles = $mux->handles;
333
334   loop
335       Enter the main loop and start processing IO events.
336
337           $mux->loop;
338
339   endloop
340       Prematurly terminate the loop.  The loop will automatically terminate
341       when there are no remaining descriptors to be watched.
342
343           $mux->endloop;
344
345   udp_peer
346       Get peer endpoint of where the last udp packet originated.
347
348           $saddr = $mux->udp_peer($fh);
349
350   is_udp
351       Sometimes UDP packets require special attention.  This method will tell
352       if a file handle is of type UDP.
353
354           $is_udp = $mux->is_udp($fh);
355
356   write
357       Send output to a file handle.
358
359           $mux->write($fh, "'ere I am, JH!\n");
360
361   shutdown
362       Shut down a socket for reading or writing or both.  See the "shutdown"
363       Perl documentation for further details.
364
365       If the shutdown is for reading, it happens immediately.  However,
366       shutdowns for writing are delayed until any pending output has been
367       successfully written to the socket.
368
369           $mux->shutdown($socket, 1);
370
371   close
372       Close a handle.  Always use this method to close a handle that is being
373       watched by the multiplexer.
374
375           $mux->close($fh);
376

CALLBACK INTERFACE

378       Callback objects should support the following interface.  You do not
379       have to provide all of these methods, just provide the ones you are
380       interested in.
381
382       All methods receive a reference to the callback object (or package) as
383       their first argument, in the traditional object oriented way.
384       References to the "IO::Multiplex" object and the relevant file handle
385       are also provided.  This will be assumed in the method descriptions.
386
387   mux_input
388       Called when input is ready on a descriptor.  It is passed a reference
389       to the input buffer.  It should remove any input that it has consumed,
390       and leave any partially received data in the buffer.
391
392           sub mux_input {
393               my $self = shift;
394               my $mux  = shift;
395               my $fh   = shift;
396               my $data = shift;
397
398               # Process each line in the input, leaving partial lines
399               # in the input buffer
400               while ($$data =~ s/^(.*?\n)//) {
401                   $self->process_command($1);
402               }
403           }
404
405   mux_eof
406       This is called when an end-of-file condition is present on the
407       descriptor.  This is does not nessecarily mean that the descriptor has
408       been closed, as the other end of a socket could have used "shutdown" to
409       close just half of the socket, leaving us free to write data back down
410       the still open half.  Like mux_input, it is also passed a reference to
411       the input buffer.  It should consume the entire buffer or else it will
412       just be lost.
413
414       In this example, we send a final reply to the other end of the socket,
415       and then shut it down for writing.  Since it is also shut down for
416       reading (implicly by the EOF condition), it will be closed once the
417       output has been sent, after which the mux_close callback will be
418       called.
419
420           sub mux_eof {
421               my $self = shift;
422               my $mux  = shift;
423               my $fh   = shift;
424
425               print $fh "Well, goodbye then!\n";
426               $mux->shutdown($fh, 1);
427           }
428
429   mux_close
430       Called when a handle has been completely closed.  At the time that
431       "mux_close" is called, the handle will have been removed from the
432       multiplexer, and untied.
433
434   mux_outbuffer_empty
435       Called after all pending output has been written to the file
436       descriptor.
437
438   mux_connection
439       Called upon a new connection being accepted on a listen socket.
440
441   mux_timeout
442       Called when a timer expires.
443

AUTHOR

445       Copyright 1999 Bruce J Keeler <bruce@gridpoint.com>
446
447       Copyright 2001-2008 Rob Brown <bbb@cpan.org>
448
449       Released under the same terms as Perl itself.
450
451       $Id: Multiplex.pm,v 1.45 2015/04/09 21:27:54 rob Exp $
452
453
454
455perl v5.32.0                      2020-07-28                  IO::Multiplex(3)
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