[R] Using Internet proxies

[ripley@stats.ox.ac.uk]

There have been quite a few questions recently about this, so I have 
tried to gather experience.  I set up a proxy using Apache2 (a very common 
server) behind our firewall and tried various authentication approaches.

One comment: all the methods return error messages when they fail.  Please 
don't report `it doesn't work' without the full details.

1) For a proxy that authenticates at most by hostname/IP address, and for
Windows users, just set up IE6 to work, and use the --internet2
command-line flag.  This worked for me (despite various claims here).

2) For a proxy that authenticates at most by hostname/IP address, the
internal download.file method works, provided you set the environment
variable http_proxy or HTTP_PROXY correctly, e.g. in ~/.Renviron.
This is almost of the same form as used by wget, but is less tolerant,
and note that setting `no_proxy' disables the proxy for all sites (unlike 
for wget).

3) If you have a proxy that demands that you enter a username/password 
combination, you can use the internal download method in R-devel: see
?download.file.

4) Installing wget and using the options(download.file.method="wget")
provides a highly tunable approach.  For Windows users, wget is still
available on http://www.stats.ox.ac.uk/pub/Rtools.

Note that none of these methods support proxies that want more advanced 
methods of authentication, e.g. Digest under HTTP/1.1.  If there are
any such proxies, please can a user provide us with a proven method.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595