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Groups > comp.os.linux.networking > #2199

Re: HTTP POST for file upload

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On 06/05/2013 07:40 PM, Josef Moellers wrote:
> Hi,
> 
> I'm trying to extend an application to upload result files to a web
> server using HTMP POST. By and large it works but the last couple of
> bytes (the last line, to be precise) does not show up in the received
> data. Maybe someone more knowing than I has an idea what I'm doing wrong.

I found the solution in RFC 1341
(<http://www.w3.org/Protocols/rfc1341/7_2_Multipart.html>:

7.2.1 Multipart: The common syntax
:
Note that the encapsulation boundary must occur at the beginning of a
line, i.e., following a CRLF, and that that initial CRLF is considered
to be part of the encapsulation boundary rather than part of the
preceding part.
:

So I changed my code to

>     snprintf(boundary, sizeof(boundary),
> "WebKitFormBoundaryePkpFF7tjBAqx29L");
>     content_length = 0;
>     content_length += fprintf(tmpfp, "\r\n------%s\r\n", boundary);
>     content_length += fprintf(tmpfp, "Content-Disposition: form-data;
> name=\"archive_name\"\r\n");
>     content_length += fprintf(tmpfp, "\r\n");
>     content_length += fprintf(tmpfp, "%s", archive_name);
>     content_length += fprintf(tmpfp, "\r\n------%s\r\n", boundary);
>     content_length += fprintf(tmpfp, "Content-Disposition: form-data;
> name=\"destination_name\"\r\n");
>     content_length += fprintf(tmpfp, "\r\n");
>     content_length += fprintf(tmpfp, "%s", remote_name);
>     content_length += fprintf(tmpfp, "\r\n------%s\r\n", boundary);
>     content_length += fprintf(tmpfp, "Content-Disposition: form-data;
> name=\"file_contents\"; filename=\"%s\"\r\n", local_name);
>     content_length += fprintf(tmpfp, "Content-Type:
> application/x-object\r\n");
>     content_length += fprintf(tmpfp, "\r\n");
>     while ((nread = fread(buffer, 1, sizeof(buffer), src)) > 0)
>     {
>     	fwrite(buffer, 1, nread, tmpfp);
> 	content_length += nread;
>     }
>     content_length += fprintf(tmpfp, "\r\n------%s--\r\n", boundary);

Apparently the Perl CGI code was tolerant and took the "}\n" as the CRLF
preceding the last boundary and dropped that!

Another problem, not related to this one, was that I had to explicitly
close the write side of the socket in order to reliably receive the
response.

Thanks for both who helped (and all who thought about the issue).

Josef

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Thread

HTTP POST for file upload Josef Moellers <josef.moellers@invalid.invalid> - 2013-06-05 19:40 +0200
  Re: HTTP POST for file upload Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2013-06-05 19:51 +0200
  Re: HTTP POST for file upload Richard Kettlewell <rjk@greenend.org.uk> - 2013-06-05 18:53 +0100
  Re: HTTP POST for file upload Josef Moellers <josef.moellers@invalid.invalid> - 2013-06-06 21:26 +0200
    Re: HTTP POST for file upload Jorgen Grahn <grahn+nntp@snipabacken.se> - 2013-06-06 21:51 +0000

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