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Re: Reuse connection in half-closed state

From: Reese Grimsley <>
Date: Tue, 4 Apr 2017 17:42:32 -0500

Sorry to drag this message thread on so long, I just have one more thing..

I've been trying to use formadd, but I must be doing something wrong. If I
try: curl_formadd(&formPost, &last, CURLFORM_COPYNAME, "metadata",
"application/json" ,CURLFORM_END); then the header for multipart/form-data
at the top disappears, and the content length becomes 0. The corresponding
response states there to be a missing content header, and disconnects. Am
I doing something wrong within the formadd? I assume the CURLFORM_COPYNAME
is for changing the name just after the content disposition header, and
that charset will be modified automatically, since I can't tell a way to do
this explicitly. Headers for the beginning of the message were set as I
have before with CURLOPT_HTTPHEADER with a slist of headers.

I can get the server to accept the message's header and boundary terms when
building the all of the post data myself, but whatever string reader is
being used server-side seems to have a problem with the formatting I have
used. I'll ask on their forums what is wrong there, as I am sure that
question is too application specific for this mailing list.

I really appreciate the help, thank you.

On Tue, Apr 4, 2017 at 4:18 PM, Daniel Stenberg <> wrote:

> On Tue, 4 Apr 2017, Reese Grimsley wrote:
> So since I am going to be using the same host, it will use the same
>> physical connection, and it will be able to send multiple independent
>> transfer?
> As I already answered this I'm not sure what else I'm going to reply when
> you ask again without adding any more specific details to the question to
> help me give a more specific answer. So: yes, maybe.
> I am confused on how to format a multipart POST request. I notice that
>> when I set the content-type to multipart/form-data, it includes its own
>> (randomly generated?) boundary term.
> It does, yes. But you're also setting that content-type header in vein
> since libcurl will set that itself for multipart formposts.
> Can this boundary term by easily changed?
> No, it can't be changed at all actually, if you want to use libcurl's
> formposting functions.
> If you think you need to set that string yourself you need to construct
> the entire post "manually" and not use libcurl's formposting functions and
> instead just send a normal "raw" posted crafted as you see fit, with the
> boundary strings, separators, headers and all.
> My main question though is how to set the fields that look to be very
>> similar to headers underneath the --"boundary" line, and then include the
>> actual message data below that.
> They're not only similar to headers, they *are* headers. Each individual
> section in a multipart post has its own set of headers. With libcurl you
> set your headers with curl_formadd()'s CURLFORM_CONTENTHEADER option.
> Should these fields be defined by some setopt function, or are they a part
>> of the message?
> libcurl will set a few when you use curl_formadd() so that each section
> becomes a valid and working part as defined in the spec, but you can extend
> that set if you want others there.
> It is supposed to look like what I have included in the last few lines of
>> this message.
> The Content-Disposition: is automatically set by libcurl (as you can see
> when you check what libcurl sends in a formpost) and the Content-Type:
> header is set for a few files (based on the extension) but you can also set
> Following these "headers" (are they considered headers, or is there a
>> better terminology?) would be a JSON formatted string of data, followed by
>> a --boundary-- line.
> That data is the contents: CURLFORM_COPYCONTENTS.
> All this is explained and there's an example, in the man page for
> curl_formadd:
> --
> /
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Received on 2017-04-05