NAME¶
LWP::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::Online
DESCRIPTION¶
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.