On Sat, 17 Dec 2005, Zibiao.Wei_at_atxinc.com wrote:

> Here is now a real question quoted from one of our customer:
> "Our proxy architecture is setup based on forwarding first-layer proxy
> servers on to a master set of proxies which make the actual connections.
> The site does not work on the first layer of proxy servers used for our
> tax field clients, but does work on our master proxies.
>
> The first layer is simply a whitelist of acceptable sites. We have added
> the following urls to this whitelist and can access the base site, but the
> test for the application fails.
>
> atxinc.com
> atxmax.com
> atxpros.com
>
>
> It looks like the application is having issues with the forwarding layer."
>
> The clients who connect to the first-layer proxy cannot access our servers
> using libcurl (through both ftp and http), but the clients who connect to
> the master proxies can. Do I need to configure proxy for libcurl?

First, libcurl has no speific support for proxies in FTP since that is not
part of the protocol. Hoever, Most FTP proxies just force a weird input set
and libcurl can do that.

libcurl has full and extensive support for HTTP proxies. If you want to
transfer HTTP via a proxy, you need to tell libcurl about it. If you do and
your customer is setting up things correctly, I seriously cannot see how this
can be libcurl's fault. Of course, given some detailed traces we can probably
start analyzing it in our ends.

> Right now I do not touch anything related to proxy in my application,
> because I do not know whether my clients use proxy or not, or how many
> layers they have.

HTTP only defines a proxy, period. If they have an advanced setup consisting
of several "layers", they need to hide that fact from the HTTP layer and thus
it should work for libcurl.

> Neither do I know how to configure proxy for libcurl if this is really
> required.

CURLOPT_PROXY, at least, is required.

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