Powerpoint upload stops at ~9MB with cURL -F
<p>I have a problem using ConvertApi.com PowerPoint2Pdf conversion, when uploading files that are larger than 9MB. I can upload at least 43MB PowerPoint files through the browser form without problems, so it should not be a restriction in the API. </p>

<p>If the size is less than this, the conversion works with curl perfectly fine, when I use this line (<a href="http://pastebin.com/zfpeHRy1" rel="nofollow">Applying these instructions, with the appropriate changes</a>):</p>

<p><code>curl -v -F file=@"filename.pptx" http://do.convertapi.com/PowerPoint2Pdf?apikey=YourApiKeyHere &gt; output.pdf</code></p>

<p><strong>Edit:</strong> <em>That command actually works, but it was broken when combined with the URL <a href="http://www.convertapi.com/powerpoint-pdf-api" rel="nofollow">found here</a></em></p>

<p>However, if I do the same with a file larger than 9MB, the curl progress meter shows that the currently uploaded amount of bytes stops growing after less than 10 seconds, with the Xferd field indicating that it has uploaded something around 9000k (in the example below, it is 9120k). Eventually the connection seems to stop every time after 2min 17s (once 2:16, tested 3 times with different >25Mb files), with the following output, or similar:</p>

<p><code>21 41.5M    0     0   21 9120k      0  67800  0:10:42  0:02:17  0:08:25     0
* Closing connection 0
curl: (56) SSL read: error:00000000:lib(0):func(0):reason(0), errno 104</code></p>

<p>The error code 56 means apparently "connection reset by peer", but this happens more than two minutes after the upload has halted, so it seems to be a healthy reaction to the problem from the server side not to wait indefinitely for the upload to continue. </p>

<p>As the similar upload works consistently without problems when using the browser form, it should not be a problem with the browser configuration, but rather with my request.</p>

<p>As I am not very familiar with curl, and my searches didn't provide me any real insights in how to upload large binary files using -F, I am not sure how I should change the request.  </p>

<p>I found a similar problem here, but there the problem seems to have been something depending on the server. <a href="https://stackoverflow.com/questions/28813853/php-curl-asp-net-c-sharp-send-files-bigger-than-9mb" title="This question">PHP / CURL / ASP.NET / C# - Send files bigger than 9mb</a></p>