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, asymtotically 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.

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.