On Wed, 17 Feb 2010, Tiberiu Motoc wrote:

> From all systems where i deployed my curl based app, there is one which
> returns "empty reply from server" curl(52). I did find one other thread on
> this newsgroup which was describing the same problem:
> http://curl.haxx.se/mail/archive-2005-01/0129.html.

I wouldn't be so sure that you have the same problem, but perhaps it is.

> The guy was able to solve it by writing a curlrc in his home directory with
> comtents User-Agent: curl. What does that solve? What does it do?

It modifies the User-Agent: field in curl's requests to that fixed string.

> I dont bage access to that system so it is difficult for me to
> investigate.

Setting the agent with CURLOPT_USERAGENT is what he did.

And no, there's no explanation, sensible or crazy, that explains why setting
the user-agent to that was a good idea for him.

In your case, as I believe you're using libcurl and not curl, it might make
sense in the way that without an explictit user-agent libcurl sends none and
perhaps there's a transparent proxy or something similarly stupid in the way
in this particular instance that requires such a field for it to be considered
a valid and fine request.

I'm speculating wildly.

-- 
  / daniel.haxx.se
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