How do I transfer a file using wininet that is readable by a php script?

I would like to transfer a text file to a webserver using wininet as if the file was being transferred using a web form that posts the file to the server.

Based on answers I've received I've tried the following code:

 static TCHAR hdrs[] = "Content-Type: multipart/form-data\nContent-Length: 25";
 static TCHAR frmdata[] = "file=filename.txt\ncontent";

   HINTERNET hSession = InternetOpen("MyAgent",
      INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);
   HINTERNET hConnect = InternetConnect(hSession, "example.com",
      INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1);
   HINTERNET hRequest = HttpOpenRequest(hConnect, "POST", "test.php", NULL, NULL, NULL, 0, 1);
   HttpSendRequest(hRequest, hdrs, strlen(hdrs), frmdata, strlen(frmdata));");

The test.php script is being run, but it doesn't appear to be getting the correct data.

Could anyone give me any additional help or somewhere to look? Thanks.

Solution

Changing the form data and headers that I had above to the following solved the problem:

  static TCHAR frmdata[] = "-----------------------------7d82751e2bc0858\nContent-Disposition: form-data; name=\"uploadedfile\"; filename=\"file.txt\"\nContent-Type: text/plain\n\nfile contents  here\n-----------------------------7d82751e2bc0858--";
  static TCHAR hdrs[] = "Content-Type: multipart/form-data; boundary=---------------------------7d82751e2bc0858";