The problem with getting file upload progress

[Eugene]

Hello,

I experience a problem with getting file upload progress through WinInet
API. I use windows task manager for monitoring network activity and it looks
like there is a few seconds delay between the first call of InternetWriteFile
function and a start of data sending.

I suppose that during the first few seconds data is cached somewhere but not
being sent, nevertheless callback function gets INTERNET_STATUS_REQUEST_SENT
notifications. After that I see some “silence” period in the callback
function calls and at this moment network monitor starts to display network
activity. So by the moment when network monitor starts to show upload process
I am reported that some data is already uploaded (about 8-50 Mb) with
INTERNET_STATUS_REQUEST_SENT notifications. The actual problem occurs when
uploading data is completely cached and I have no idea how much data was
really uploaded.

Is there another way to get uploading progress or maybe I do something wrong?

The problem can be reproduced with Asynchronous Example:

http://msdn.microsoft.com/en-us/library/cc185683(VS.85).aspx

Best regards,
Eugene