On Wed, 11 Feb 2009, Ranu Gontia wrote:

>> < HTTP/1.1 407 Proxy Authentication Required ( The ISA Server requires
>> authoriza
>>
>> < Proxy-Authenticate: Negotiate
>> < Proxy-Authenticate: Kerberos
>> < Proxy-Authenticate: NTLM

...

> curl_easy_setopt(curlhandle, CURLOPT_PROXYAUTH, CURLAUTH_BASIC);

The proxy says it wants Negotiate, Kerberos or NTLM authentication. You
explicitly tell libcurl to use Basic. I doubt you'll win.

> If I specify that I am using proxy tunnel
> i.e. curl_easy_setopt(curlhandle, CURLOPT_HTTPPROXYTUNNEL, 1);
> then following error comes -:

But why are you using CURLOPT_HTTPPROXYTUNNEL? Do you even understand what it
does? The 502 proxy response should be a hint you're not allowed to tunnel
through the proxy to port 21 on the "outside".

-- 
  / daniel.haxx.se