1POE(3) User Contributed Perl Documentation POE(3)
2
6 POE - portable multitasking and networking framework for any event loop
7
9 #!/usr/bin/perl -w
10 use strict;
11 use POE; # Auto-includes POE::Kernel and POE::Session.
13 sub handler_start {
15 my ($kernel, $heap, $session) = @_[KERNEL, HEAP, SESSION];
16 print "Session ", $session->ID, " has started.\n";
17 $heap->{count} = 0;
18 $kernel->yield('increment');
19 }
20 sub handler_increment {
22 my ($kernel, $heap, $session) = @_[KERNEL, HEAP, SESSION];
23 print "Session ", $session->ID, " counted to ", ++$heap->{count}, ".\n";
24 $kernel->yield('increment') if $heap->{count} < 10;
25 }
26 sub handler_stop {
28 print "Session ", $_[SESSION]->ID, " has stopped.\n";
29 }
30 for (1..10) {
32 POE::Session->create(
33 inline_states => {
34 _start => \&handler_start,
35 increment => \&handler_increment,
36 _stop => \&handler_stop,
37 }
38 );
39 }
40 POE::Kernel->run();
42 exit;
43
45 POE is a framework for cooperative, event driven multitasking and
46 networking in Perl. Other languages have similar frameworks. Python
47 has Twisted. TCL has "the event loop".
48 POE provides a unified interface for several other event loops,
50 including select(), IO::Poll, Glib, Gtk, Tk, Wx, and Gtk2. Many of
51 these event loop interfaces were written by others, with the help of
52 POE::Test::Loops. They may be found on the CPAN.
53 POE achieves its its high degree of portability to different operating
55 systems and Perl versions by being written entirely in Perl. CPAN
56 hosts optional XS modules for POE if speed is more desirable than
57 portability.
58 POE is designed in layers. Each layer builds atop the lower level
60 ones. Programs are free to use POE at any level of abstraction, and
61 different levels can be mixed and matched seamlessly within a single
62 program. Remember, though, that higher-level abstractions often
63 require more resources than lower-level ones. The conveniences they
64 provide are not free.
65 POE's bundled abstraction layers are the tip of a growing iceberg.
67 Sprocket, POE::Stage, and other CPAN distributions build upon this
68 work. You're encouraged to look around.
69 No matter how high you go, though, it all boils down to calls to
71 POE::Kernel. So your down-to-earth code can easily cooperate with
72 stratospheric systems.
73 Layer 1: Kernel and Sessions
75 The lowest public layer is comprised of POE::Kernel, POE::Session, and
76 other session types.
77 POE::Kernel does most of the heavy lifting. It provides a portable
79 interface for filehandle activity detection, multiple alarms and other
80 timers, signal handling, and other less-common features.
81 POE::Session and derived classes encapsulate the notion of an event
83 driven task. They also customize event dispatch to a particular
84 calling convention. POE::NFA, for example, is more of a proper state
85 machine. The CPAN has several other kinds of sessions.
86 Everything ultimately builds on these classes or the concepts they
88 implement. If you're short on time, the things to read besides this
89 are POE::Kernel and POE::Session.
90 Layer 2: Wheels, Filters, and Drivers
92 POE::Wheel objects are dynamic mix-ins for POE::Session instances.
93 These "wheels" perform very common, generic tasks in a highly reusable
94 and customizable way. POE::Wheel::ReadWrite, for example, implements
95 non-blocking buffered I/O. Nearly everybody needs this, so why require
96 people to reinvent it all the time?
97 POE::Filter objects customize wheels in a modular way. Filters act as
99 I/O layers, turning raw streams into structured data, and serializing
100 structures into something suitable for streams. The CPAN also has
101 several of these.
102 Drivers are where the wheels meet the road. In this case, the road is
104 some type of file handle. Drivers do the actual reading and writing in
105 a standard way so wheels don't need to know the difference between
106 send() and syswrite().
107 POE::Driver objects get relatively short shrift because very few are
109 needed. The most common driver, POE::Driver::SysRW is ubiquitous and
110 also the default, so most people will never need to specify one.
111 Layer 3: Components
113 POE::Component classes are essentially Perl classes that use POE to
114 perform tasks in a non-blocking or cooperative way. This is a very
115 broad definition, and POE components are all over the abstraction map.
116 Many components, such as POE::Component::Server::SMTP, encapsulate the
118 generic details of an entire application. Others perform rather narrow
119 tasks, such as POE::Component::DirWatch::Object.
120 POE components are often just plain Perl objects. The previously
122 mentioned POE::Component::DirWatch::Object uses Moose. Other object
123 and meta-object frameworks are compatible.
124 Also of interest is POE::Component::Generic, which is allows you to
126 create a POE component from nearly nearly any blocking module.
127 There are quite a lot of components on the CPAN.
129 <http://search.cpan.org/search?query=poe+component&mode=all>
130 Layer 4 and Beyond: Frameworks and Object Metaphors
132 It's possible to abstract POE entirely behind a different framework.
133 In fact we encourage people to write domain-specific abstractions that
134 entirely hide POE if necessary. The nice thing here is that even at
135 these high levels of abstraction, things will continue to interoperate
136 all the way down to layer 1.
137 Two examples of ultra-high level abstraction are Sprocket, a networking
139 framework that does its own thing, and POE::Stage, which is POE's
140 creator's attempt to formalize and standardize POE components.
141 It is also possible to communicate between POE processes. This is
143 called IKC, for Inter-Kernel Communication. There are a few IKC
144 components on the CPAN
145 (<http://search.cpan.org/search?query=IKC&mode=all>), notably
146 POE::Component::IKC and POE::TIKC.
147 Layer 0: POE's Internals
149 POE's layered architecture continues below the surface. POE's guts are
150 broken into specific POE::Loop classes for each event loop it supports.
151 Internals are divided up by type, giving POE::Resource classes for
152 Aliases, Controls, Events, Extrefs, FileHandles, SIDs, Sessions,
153 Signals, and Statistics.
154 POE::Kernel's APIs are extensible through POE::API mix-in classes.
156 Some brave souls have even published new APIs on CPAN, such as
157 POE::API::Peek (which gives you access to some of the internal
158 POE::Resource methods).
159 By design, it's possible to implement new POE::Kernel guts by creating
161 another POE::Resource class. One can then expose the functionality
162 with a new POE::API mix-in.
163
165 You're reading the main POE documentation. It's the general entry
166 point to the world of POE. You already know this, however, so let's
167 talk about something more interesting.
168 Basic Features
170 POE's basic features are documented mainly in POE::Kernel and
171 POE::Session. Methods are documented in the classes that implement
172 them. Broader concepts are covered in the most appropriate class, and
173 sometimes they are divided among classes that share in their
174 implementation.
175 Basic Usage
177 Basic usage, even for POE.pm, is documented in POE::Kernel. That's
178 where most of POE's work is done, and POE.pm is little more than a
179 class loader.
180 @_[KERNEL, HEAP, etc.]
182 Event handler calling conventions, that weird @_[KERNEL, HEAP] stuff,
183 is documented in POE::Session. That's because POE::Session implements
184 the calling convention, and other session types often do it
185 differently.
186 Base Classes Document Common Features
188 The POE::Wheel, POE::Driver, POE::Filter, and POE::Component base
189 classes describe what's common among each class. It's a good idea to
190 at least skim the base class documentation since the subclasses tend
191 not to rehash the common things.
192 POE::Queue, POE::Resource, POE::Loop, and POE::API document the
194 concepts and sometimes the standard interfaces behind multiple
195 subclasses. You're encouraged to have a look.
196 Helper Classes
198 POE includes some helper classes for portability. POE::Pipe, and its
199 subclasses POE::Pipe::OneWay and POE::Pipe::TwoWay are portable pipes.
200 Event Loop Bridges
202 POE::Loop documents and specifies the interface for all of POE's event
203 loop bridges. The individual classes may document specific details,
204 but generally they adhere to the spec strongly enough that they don't
205 need to.
206 Many of the existing POE::Loop bridges provided in POE's base
208 distribution will move out to separate distributions shortly. The
209 documentation will probably remain the same, however.
210 POE::Queue and POE::Queue::Array
212 POE's event queue is basically a priority heap implemented as an
213 ordered array. POE::Queue documents the standard interface for POE
214 event queues, and POE::Queue::Array implements the ordered array queue.
215 Tony Cook has released POE::XS::Queue::Array, which is a drop-in C
216 replacement for POE::Queue::Array. You might give it a try if you need
217 more performance. POE's event queue is some of the hottest code in the
218 system.
219 This Section Isn't Complete
221 Help organize the documentation. Obviously we can't think of
222 everything. We're well aware of this and welcome audience
223 participation.
224 See SEE ALSO
226 Wherever possible, the SEE ALSO section will cross-reference one module
227 to related ones.
228 Don't Forget the Web
230 Finally, there are many POE resources on the web. The CPAN contains a
231 growing number of POE modules. <http://poe.perl.org/> hosts POE's
232 wiki, which includes tutorials, an extensive set of examples,
233 documentation, and more. Plus it's a wiki, so you can trivially pitch
234 in your two cents.
235
237 POE's basic requirements are rather light. Most are included with
238 modern versions of Perl, and the rest (if any) should be generally
239 portable by now.
240 Time::HiRes is highly recommended, even for older Perls that don't
242 include it. POE will work without it, but alarms and other features
243 will be much more accurate if it's included. POE::Kernel will use
244 Time::HiRes automatically if it's available.
245 POE::Filter::Reference needs a module to serialize data for
247 transporting it across a network. It will use Storable, FreezeThaw,
248 YAML, or some other package with freeze() and thaw() methods. It can
249 also use Compress::Zlib to conserve bandwidth and reduce latency over
250 slow links, but it's not required.
251 If you want to write web servers, you'll need to install libwww-perl,
253 which requires libnet. This is a small world of modules that includes
254 HTTP::Status, HTTP::Request, HTTP::Date, and HTTP::Response. They are
255 generally good to have, and modern versions of Perl even include them.
256 Programs that use POE::Wheel::Curses will of course require the Curses
258 module, which in turn requires some sort of curses library.
259 If you're using POE with Tk, you'll need Tk installed.
261 And other obvious things. Let us know if we've overlooked a non-
263 obvious detail.
264
266 One of POE's design goals is to be as portable as possible. That's why
267 it's written in "Plain Perl". XS versions of POE modules are available
268 as third-party distributions. Parts of POE that require nonstandard
269 libraries are optional, and not having those libraries should not
270 prevent POE from installing.
271 Despite Chris Williams' efforts, we can't test POE everywhere. Please
273 see the GETTING HELP section if you run into a problem.
274 POE is expected to work on most forms of UNIX, including FreeBSD, MacOS
276 X, Linux, Solaris. Maybe even AIX and QNX, but we're not sure.
277 POE is also tested on Windows XP, using the latest version of
279 ActiveState, Strawberry and Cygwin Perl. POE is fully supported with
280 Strawberry Perl, as it's included in the Strawberry distribution.
281 OS/2 and MacOS 9 have been reported to work in the past, but nobody
283 seems to be testing there anymore. Reports and patches are still
284 welcome.
285 Past versions of POE have been tested with Perl versions as far back as
287 5.004_03 and as recent as "blead", today's development build. We can
288 no longer guarantee each release will work everywhere, but we will be
289 happy to work with you if you need special support for a really old
290 system.
291 POE's quality is due in large part to the fine work of Chris Williams
293 and the other CPAN testers. They have dedicated resources towards
294 ensuring CPAN distributions pass their own tests, and we watch their
295 reports religiously. You can, too. The latest POE test reports can be
296 found at <http://cpantesters.org/distro/P/POE.html>.
297 Thanks also go out to Benjamin Smith and the 2006 Google Summer of
299 Code. Ben was awarded a grant to improve POE's test suite, which he
300 did admirably.
301 Windows Issues
303 POE seems to work very nicely with Perl compiled for Cygwin. If you
304 must use ActiveState Perl, please use the absolute latest version.
305 ActiveState Perl's compatibility fluctuates from one build to another,
306 so we tend not to support older releases.
307 Windows and ActiveState Perl are considered an esoteric platform due to
309 the complex interactions between various versions. POE therefore
310 relies on user feedback and support here.
311 A number of people have helped bring POE's Windows support this far,
313 through contributions of time, patches, and other resources. Some of
314 them are: Sean Puckett, Douglas Couch, Andrew Chen, Uhlarik Ondoej,
315 Nick Williams, and Chris Williams (no relation).
316 Other Compatibility Issues
318 None currently known. See GETTING HELP below if you've run into
319 something.
320
322 POE's developers take pride in its quality. If you encounter a
323 problem, please let us know.
324 POE's Request Tracker
326 You're welcome to e-mail questions and bug reports to
327 <bug-POE@rt.cpan.org>. This is not a realtime support channel, though.
328 If you need a more immediate response, try one of the methods below.
329 POE's Mailing List
331 POE has a dedicated mailing list where developers and users discuss the
332 software and its use. You're welcome to join us. Send an e-mail to
333 <poe-help@perl.org> for subscription instructions. The subject and
334 message body are ignored.
335 POE's Web Site
337 <http://poe.perl.org> contains recent information, tutorials, and
338 examples. It's also a wiki, so people are invited to share tips and
339 code snippets there as well.
340 POE's Source Code
342 The following command will fetch the most current version of POE into
343 the "poe" subdirectory:
344 svn co https://poe.svn.sourceforge.net/svnroot/poe poe
346 SourceForge
348 http://sourceforge.net/projects/poe/ is POE's project page.
349 Internet Relay Chat (IRC)
351 irc.perl.org channel #poe is an informal place to waste some time and
352 maybe even discuss Perl and POE. Consider an SSH relay if your
353 workplace frowns on IRC. But only if they won't fire you if you're
354 caught.
355 Personal Support
357 Unfortunately we don't have resources to provide free one-on-one
358 personal support anymore. We'll do it for a fee, though. Send Rocco
359 an e-mail via his CPAN address.
360
362 Broken down by abstraction layer.
363 Layer 1
365 POE::Kernel, POE::Session, POE::NFA
366 Layer 2
368 POE::Wheel, POE::Wheel::Curses, POE::Wheel::FollowTail,
369 POE::Wheel::ListenAccept, POE::Wheel::ReadLine, POE::Wheel::ReadWrite,
370 POE::Wheel::Run, POE::Wheel::SocketFactory
371 POE::Driver, POE::Driver::SysRW
373 POE::Filter, POE::Filter::Block, POE::Filter::Grep, POE::Filter::HTTPD,
375 POE::Filter::Line, POE::Filter::Map, POE::Filter::RecordBlock,
376 POE::Filter::Reference, POE::Filter::Stackable, POE::Filter::Stream
377 Layer 3
379 POE::Component, POE::Component::Client::TCP,
380 POE::Component::Server::TCP
381 Layer 0
383 POE::Loop, POE::Loop::Event, POE::Loop::Gtk, POE::Loop::IO_Poll,
384 POE::Loop::Select, POE::Loop::Tk
385 POE::Queue, POE::Queue::Array
387 POE::Resource, POE::Resource::Aliases, POE::Resource::Events,
389 POE::Resource::Extrefs, POE::Resource::FileHandles,
390 POE::Resource::Performance, POE::Resource::SIDs,
391 POE::Resource::Sessions, POE::Resource::Signals
392 Helpers
394 POE::Pipe, POE::Pipe::OneWay, POE::Pipe::TwoWay
395 Home Page
397 http://poe.perl.org/
398 Bug Tracker
400 https://rt.cpan.org/Dist/Display.html?Status=Active&Queue=POE
401 Repository
403 https://poe.svn.sourceforge.net/svnroot/poe/trunk/poe
404 Other Resources
406 http://search.cpan.org/dist/POE/
407
409 POE is the combined effort of quite a lot of people. This is an
410 incomplete list of some early contributors. A more complete list can
411 be found in POE's change log.
412 Ann Barcomb
414 Ann Barcomb is <kudra@domaintje.com>, aka "kudra". Ann contributed
415 large portions of POE::Simple and the code that became the ReadWrite
416 support in POE::Component::Server::TCP. Her ideas also inspired
417 Client::TCP component, introduced in version 0.1702.
418 Artur Bergman
420 Artur Bergman is <sky@cpan.org>. He contributed many hours' work
421 into POE and quite a lot of ideas. Years later, I decide he's right
422 and actually implement them.
423 Artur is the author of Filter::HTTPD and Filter::Reference, as well
425 as bits and pieces throughout POE. His feedback, testing, design and
426 inspiration have been instrumental in making POE what it is today.
427 Artur is investing his time heavily into perl 5's iThreads and PONIE
429 at the moment. This project has far-reaching implications for POE's
430 future.
431 Jos Boumans
433 Jos Boumans is <kane@cpan.org>, aka "kane". Jos is a major driving
434 force behind the POE::Simple movement and has helped inspire the
435 POE::Components for TCP clients and servers.
436 Matt Cashner
438 Matt Cashner is <sungo@pobox.com>, aka "sungo". Matt is one of POE's
439 core developers. He's spearheaded the movement to simplify POE for
440 new users, flattening the learning curve and making the system more
441 accessible to everyone. He uses the system in mission critical
442 applications, folding feedback and features back into the
443 distribution for everyone's enjoyment.
444 Andrew Chen
446 Andrew Chen is <achen-poe@micropixel.com>. Andrew is the resident
447 POE/Windows guru. He contributes much needed testing for Solaris on
448 the SPARC and Windows on various Intel platforms.
449 Douglas Couch
451 Douglas Couch is <dscouch@purdue.edu>. Douglas helped port and
452 maintain POE for Windows early on.
453 Jeffrey Goff
455 Jeffrey Goff is <jgoff@blackboard.com>. Jeffrey is the author of
456 several POE modules, including a tokenizing filter and a component
457 for managing user information, PoCo::UserBase. He's also co-author
458 of "A Beginner's Introduction to POE" at www.perl.com.
459 Philip Gwyn
461 Philip Gwyn is <gwynp@artware.qc.ca>. He extended the Wheels I/O
462 abstraction to support hot-swappable filters, and he eventually
463 convinced Rocco that unique session and kernel IDs were a good thing.
464 Philip also enhanced POE::Filter::Reference to support different
466 serialization methods. He has also improved POE's quality by finding
467 and fixing several bugs. He provided POE a much needed code review
468 around version 0.06.
469 Lately, Philip tracked down the race condition in signal handling and
471 fixed it with the signal pipe.
472 Arnar M. Hrafnkelsson
474 Arnar is <addi@umich.edu>. Addi tested POE and POE::Component::IRC
475 on Windows, finding bugs and testing fixes. He appears throughout
476 the Changes file. He has also written "cpoe", which is a POE-like
477 library for C.
478 Dave Paris
480 Dave Paris is <dparis@w3works.com>. Dave tested and benchmarked POE
481 around version 0.05, discovering some subtle (and not so subtle)
482 timing problems. The pre-forking server sample was his idea.
483 Versions 0.06 and later scaled to higher loads because of his work.
484 He has contributed a lot of testing and feedback, much of which is
485 tagged in the Changes file as a-mused. The man is scarily good at
486 testing and troubleshooting.
487 Dieter Pearcey
489 Dieter Pearcey is <dieter@bullfrog.perlhacker.org>. He goes by
490 several Japanese nicknames. Dieter's current area of expertise is in
491 Wheels and Filters. He greatly improved POE::Wheel::FollowTail, and
492 his Filter contributions include the basic Block filter, as well as
493 Stackable, RecordBlock, Grep and Map.
494 Robert Seifer
496 Robert Seifer is <e-mail unknown>. He rotates IRC nicknames
497 regularly.
498 Robert contributed entirely too much time, both his own and his
500 computers, towards the detection and eradication of a memory
501 corruption bug that POE tickled in earlier Perl versions. In the
502 end, his work produced a simple compile-time hack that worked around
503 a problem relating to anonymous subs, scope and @{} processing.
504 Matt Sergeant
506 Matt contributed POE::Kernel::Poll, a more efficient way to watch
507 multiple files than select(). It's since been moved to
508 POE::Loop::IO_Poll.
509 Richard Soderberg
511 Richard Soderberg is <poe@crystalflame.net>, aka "coral". Richard is
512 a collaborator on several side projects involving POE. His work
513 provides valuable testing and feedback from a user's point of view.
514 Dennis Taylor
516 Dennis Taylor is <dennis@funkplanet.com>. Dennis has been testing,
517 debugging and patching bits here and there, such as Filter::Line
518 which he improved by leaps in 0.1102. He's also the author of
519 POE::Component::IRC, the widely popular POE-based successor to his
520 wildly popular Net::IRC library.
521 David Davis
523 David Davis, aka Xantus is <xantus@cpan.org>. David contributed
524 patches to the HTTPD filter, and added CALLER_STATE to POE::Session.
525 He is the author of Sprocket, a networking framework built on POE.
526 Others?
528 Please contact the author if you've been forgotten and would like to
529 be included here.
530 TODO - This section has fallen into disrepair. A POE historian needs
532 to cull the CHANGES for the names of major contributors.
533 Author
535 Rocco Caputo
536 Rocco Caputo is <rcaputo@cpan.org>. POE is his brainchild. He
537 wishes to thank you for your interest, and he has more thanks than he
538 can count for all the people who have contributed. POE would not be
539 nearly as cool without you.
540 Except where otherwise noted, POE is Copyright 1998-2009 Rocco
542 Caputo. All rights reserved. POE is free software; you may
543 redistribute it and/or modify it under the same terms as Perl itself.
544 Thank you for reading!
546perl v5.12.1 2010-04-03 POE(3)