[Rd] Cross-platform check for internet connection

[hadley wickham]

On 6/22/07, Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:
> On Fri, 22 Jun 2007, hadley wickham wrote:
>
> > What's the recommended way to check if an internet connection is
> > available across platforms?  I was using is.null(nsl()) but this does
> > not work on windows.
>
> I don't know a way to do this on Windows without a possible very long
> hang.  It's complicated by the use of two alternative internet connection
> mechanisms on Windows and having little control over the IE-based one.
>
> Another issue is software firewalls: they can take many minutes to
> decide to let a new program talk to the Internet if they 'call home' to
> ask advice.

Thanks for those details, I hadn't considered the problems that might
be associated with firewalls.

To give a little more context, I have an example in one of my packages
which downloads some data off the web.  I don't really want to include
the data in my package, since it's not my data (although I'm fairly
certain I could get permission to include it).

So really it doesn't matter if there will be a long delay, provided
that there won't be a long delay for the windows CRAN server.  I could
wrap the entire example in dontrun, but then that loses the useful
checking I get locally when running r cmd check.

Are there any other solutions?

Thanks,

Hadley