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Table of Contents; About POE; Compatibility (Non-Requirements and
Requirements); Availability; Support Resources; Installing and
Testing; The Future
"POE" is an acronym for Perl Object Environment. This may change to
Persistent Object Environment.
First and foremost, it is a programming framework for event-driven
state machines.
POE includes high-level, functional interfaces for select, alarms,
sockets and file I/O. The interfaces are robust but incomplete.
From different vantage points, POE may look like other things:
It may seem to be a cooperative multithreading model.
It may be interpreted as a portable component architecture.
Because it implements a low-level programming concept, POE can do many
POE has been tested with as many Perl versions as the author (and
testing pool) can find. This includes Linux, FreeBSD, and OS/2, all
of which support enough of POSIX to run POE. It is known to work with
older Perl versions, back to 5.004_03 (maybe earlier). It should also
work with the latest stable release (the latest development release
may also work). For the most recent compatibility results, see
If you have news about breakage or success that's not documented,
please let me know. Thank you!
The half-tested Windows support that was removed in 0.0806 turns out
to be necessary and useful. It was put back in version 0.0807, and at
least one Windows user, Douglas Couch <!dscouch>, has found
joy using POE.
As of this writing, Doug reports that POE works with the latest stable
ActivePerl, prior to (but not including) version 5.6. He says that
the 5.6 version includes fork() and other Unix compatibilities, but it
still definitely seems to be beta level code.
He writes:
I've done some preliminary testing of the 0.0903 version and the
re-addition of the Win32 support seems to be a success. I'll do
some more intensive testing in the next few days to make sure
nothing else is broken that I haven't missed.
And later:
After testing out my own program and having no problems with the
newest version (with Win32 support), I thought I'd test out some of
the samples and relay my results.
filterchange.perl and preforkedserver.perl both contain fork
commands which are still unsupported by ActiveState's port of Perl,
so they were both unsuccessful. (this was anticipated for anything
containing fork)
ref-type.perl, refsender.perl, thrash.perl and wheels2.perl all ran
up against the same unsupported POSIX macro. According to the error
message, my vendor's POSIX doesn't support the macro EINPROGRESS ...q
Other than those particular problems all of the other sample scripts
ran fine.
And later, after it was suggested to remove the EINPROGRESS code:
> ... and running something that connects to an outbound server,
> such as samples/proxy.perl. The normal "connection in progress"
> state will become a failure, and the proxy will die in "connect"
> with an error number and name.
Ummmm... would you believe I did this and couldn't get it to break?
I think I need to play a bit with the proxy settings in the sample,
I couldn't make it do an http proxy, but I also couldn't make it
... so I made EINPROGRESS a dummy thing on Win32. Let me know if
there's breakage!
P.S.: If you've just skipped ahead to read about Windows, you should
skip back one section, to the General compatibility information, which
may still apply.
Macintosh users have rumored that POE might work on MacOS, but none of
them have stepped forward with actual failure or success reports. It
would be greatly appreciated if someone could confirm or deny
something. Anything. Bueller?
POE is compatible with fork(), but it is only used upon request. This
distribution includes a sample server that uses a pool of forked
POE will use Time::HiRes, if it's available. Nothing untoward should
happen if it's not, unless you use one of the sample programs that
absolutely requires it.
POE currently uses no XS in its implementation. It should work
wherever a sufficiently complete version of Perl does.
For portability, POE uses POSIX system calls and constants. There
should be no problem running it on systems that have sufficient POSIX
Some of POE's sample programs require a recent IO bundle, but you get
that for free with recent versions of Perl.
Filter::Reference requires either Storable, FreezeThaw or some other
freeze/thaw package. Storable tends to be fastest, and it's checked
first. The Reference filter can also use Compress::Zlib upon request,
but it works without it too.
Filter::HTTPD requires a small world of modules: HTTP::Status;
HTTP::Request; HTTP::Date and URI::URL.
The httpd.perl sample program uses Filter::HTTPD, which uses all that
other stuff.
The preforkedserver.perl sample program uses POE::Kernel::fork(),
which in turn uses the fork() built-in. This may or may not be
available on your planet.
Other sample programs may require other modules, but the required
modules aren't required if you don't require those specific features.
The latest stable release of POE is available three ways:
``perl -MCPAN -e shell'' Then type ``install POE'' at the CPAN
In the /authors/id/R/RC/RCAPUTO/ on your favorite CPAN mirror. This
is where the CPAN shell gets it.
If you don't have a favorite CPAN mirror, you really ought to pick
one. You can download and manually install the latest stable POE
from <> until then.
Beta versions of the next release are available from the author.
They tend to be mostly stable, and other module and program authors
tend to use them because they're incrementally better than what's on
the CPAN.
Relatively stable betas are available from the POE web page, at
Places on the Internet where you can find more information about POE:
POE has a mailing list thanks to Arturn Bergman. You may subscribe to
it by sending e-mail:
From: (the address to which you want your mail sent)
Subject: (anything will do)
Anything will do for the body.
All forms of feedback are welcome.
POE has a web site thanks to Johnathan Vail. The latest POE
development snapshot, along with the Changes file and some other stuff
can be found at <>.
If you've been using POE since before 0.06, please, PLEASE read the
Changes file before installing. Many things have been broken between
versions 0.05 and 0.06.
To build and test this distribution, type:
perl Makefile.PL
make test
Actually, 'make test' doesn't do anything important. The closest
thing to real tests are the programs in the 'samples' directory.
These show how to use various bits of POE, exercising each as a side
Once everything looks good, POE can be installed by typing:
make install
-- Rocco Caputo / / Thank you for reading.
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