LWP::Online(3) User Contributed Perl Documentation LWP::Online(3)NAMELWP::Online - Does your process have access to the web
SYNOPSIS
use LWP::Online 'online';
# "Is the internet working?"
die "NO INTARWWEB!!!" unless online();
# The above means something like this
unless ( online('http') ) {
die "No basic http access to the web";
}
# Special syntax for use in test scripts that need
# "real" access to the internet. Scripts will automatically
# skip if connection fails.
use LWP::Online ':skip_all';
use Test::More tests => 4; #after LWP::OnlineDESCRIPTION
This module attempts to answer, as accurately as it can, one of the
nastiest technical questions there is.
Am I on the internet?
The answer is useful in a wide range of decisions. For example...
Should my test scripts run the online portion of the tests or just skip
them?
Do I try to fetch fresh data from the server?
If my request to the server breaks, is it because I'm offline, or
because the server is offline?
And so on, and so forth.
But a host of networking and security issues make this problem very
difficult. There are firewalls, proxies (both well behaved and badly
behaved). We might not have DNS. We might not have a network card at
all!
You might have network access, but only to a for-money wireless network
that responds to ever HTTP request with a page asking you to enter your
credit card details for paid access. Which means you don't "REALLY"
have access.
The mere nature of the question makes it practically unsolvable.
But with the answer being so useful, and the only other alternative
being to ask the user "duh... are you online?" (when you might not have
a user at all) it's my gut feeling that it is worthwhile at least
making an attempt to solve the problem, if only in a limited way.
Why LWP::Online? Why not Net::Online?
The nice thing about LWP::Online is that LWP deals with a whole range
of different transports, and is very commonly installed. HTTP, HTTPS,
FTP, and so on and so forth.
Attempting to do a more generalised Net::Online that might also check
for SSH and so on would end up most likely having to install a whole
bunch of modules that you most likely will never use.
So LWP forms a nice base on which to write a module that covers most of
the situations in which you might care, while keeping the dependency
overhead down to a minimum.
Scope
"Am I online?" is inherently an Open Problem.
That is, it's a problem that had no clean permanent solution, and for
which you could just keep writing more and more functionality
indefinitely, asymtopically approaching 100% correctness but never
reaching it.
And so this module is intended to do as good a job as possible, without
having to resort to asking any human questions (who may well get it
wrong anyway), and limiting itself to a finite amount of programming
work and a reasonable level of memory overhead to load the code.
It is thus understood the module will never be perfect, and that if any
new functionality is desired, it needs to be able to implemented by the
person that desires the new behaviour, and in a reasonably small amount
of additional code.
This module is also not intended to compensate for malicious behaviour
of any kind, it is quite possible that some malicious person might
proxy fake versions of sites that pass our content checks and then
proceed to show you other bad pages.
Test Mode
use LWP::Online ':skip_all';
As a convenience when writing tests scripts base on Test::More, the
special ':skip_all' param can be provided when loading LWP::Online.
This implements the functional equivalent of the following.
BEGIN {
require Test::More;
unless ( LWP::Online::online() ) {
Test::More->import(
skip_all => 'Test requires a working internet connection'
);
}
}
The :skip_all special import flag can be mixed with regular imports.
FUNCTIONS
online
# Default check (uses http)
online() or die "No Internet";
# The above is equivalent to
online('http') or die "No Internet";
The importable online function is the main functionality provided by
LWP::Online. It takes a single optional transport name ('http' by
default) and checks that LWP connectivity is available for that
transport.
Because it is intended as a Do What You Mean function, it checks not
only that a network connection is available, and http requests return
content, but also that it returns the CORRECT content instead of
unexpected content supplied by a man in the middle.
For example, many wireless connections require login or payment, and
will return a service provider page for any URI that you attempt to
fetch.
The set of websites used for the testing is the Google, Amazon, Yahoo
and CNN websites. The check is for a copyright statement on their
homepage, and the function returns true as soon as two of the website
return correctly, making the method relatively redundant.
Returns true if the computer is "online" (has a working connection via
LWP) or false if not.
offline
The importable offline function is provided as a convenience.
It provides a simple pass-through (including any params) to the online
function, but with a negated result.
TO DO
- Add more transport types that can be checked, somehow keeping the
code growth under control.
SUPPORT
This module is stored in an Open Repository at the following address.
http://svn.ali.as/cpan/trunk/LWP-Online
<http://svn.ali.as/cpan/trunk/LWP-Online>
Write access to the repository is made available automatically to any
published CPAN author, and to most other volunteers on request.
If you are able to submit your bug report in the form of new (failing)
unit tests (which for this module will be extremely difficult), or can
apply your fix directly instead of submitting a patch, you are strongly
encouraged to do so as the author currently maintains over 100 modules
and it can take some time to deal with non-Critical bug reports or
patches.
This will guarentee that your issue will be addressed in the next
release of the module.
If you cannot provide a direct test or fix, or don't have time to do
so, then regular bug reports are still accepted and appreciated via the
CPAN bug tracker.
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=LWP-Online
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=LWP-Online>
For other issues, for commercial enhancement or support, or to have
your write access enabled for the repository, contact the author at the
email address above.
AUTHOR
Adam Kennedy <adamk@cpan.org>
SEE ALSO
LWP::Simple
COPYRIGHT
Copyright 2006 - 2011 Adam Kennedy.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included
with this module.
perl v5.14.1 2011-07-08 LWP::Online(3)
