Why is the server sending an http 200 response instead of expected 206? - http

Question

History:
We are delivering .mp4 video via http partial request streaming. It works fine except on iPad/iPhone and we have followed all of the recommended procedures for encoding .mp4 files for iOS devices so the issue is not the files themselves. The video files are stored outside of the root of the web server so we have written code to open and stream the video upon request. Our testing has brought us to the point of comparing the headers of our "streamed" video (working but not in IOS) and linking directly to the file (working in all instances but not a possible solution as we need to store files outside of web root). Here is a comparison of the working vs. non-working headers.
link direct to file (working for IOS):
request 1
Status Code 200 OK
Accept-Ranges:bytes
Content-Length:62086289
Content-Type:video/mp4
Date:Sun, 26 Jul 2015 08:11:15 GMT
ETag:"60be3570ae7ed01:0"
Last-Modified:Fri, 24 Apr 2015 16:48:06 GMT
Server:Microsoft-IIS/7.0
X-Powered-By:ASP.NET
request 2
Status Code:206 Partial Content
Accept-Ranges:bytes
Content-Length:62086289
Content-Range:bytes 0-62086288/62086289
Content-Type:video/mp4
Date:Sun, 26 Jul 2015 08:11:16 GMT
ETag:"60be3570ae7ed01:0"
Last-Modified:Fri, 24 Apr 2015 16:48:06 GMT
Server:Microsoft-IIS/7.0
X-Powered-By:ASP.NET
opening file for streaming (not working for IOS)
request 1
Status Code 200 OK
Accept-Ranges:bytes
Cache-Control:private
Content-Length:62086289
Content-Range:bytes 0-62086289/62086289
Content-Type:video/mp4
Date:Sun, 26 Jul 2015 16:55:22 GMT
Server:Microsoft-IIS/7.0
X-AspNet-Version:4.0.30319
X-Powered-By:ASP.NET
request 2
Status Code 200 OK
Accept-Ranges:bytes
Cache-Control:private
Content-Length:62086289
Content-Range:bytes 0-62086289/62086289
Content-Type:video/mp4
Date:Sun, 26 Jul 2015 16:55:22 GMT
Server:Microsoft-IIS/7.0
X-AspNet-Version:4.0.30319
X-Powered-By:ASP.NET
Notice that the non working version's second request stays at Status Code 200 and does not change to 206. This is what we are focusing on as possibly being the issue but are at a loss. Below is the code to open the file and send to server. Note the way we are setting up the header.
Dim iStream As System.IO.Stream
' Buffer to read 10K bytes in chunk:
Dim buffer(10000) As Byte
' Length of the file:
Dim length As Integer=0
' Total bytes to read:
Dim dataToRead As Long=0
Dim isPartialFile As Boolean = False
Dim totalDelivered As Long = 0
Dim totalFileSize As Long = 0
Dim filename As String
filename = fileID & file.Extension
iStream = New System.IO.FileStream(filePath, System.IO.FileMode.Open,IO.FileAccess.Read, IO.FileShare.Read)
' Total bytes to read:
dataToRead = iStream.Length
totalFileSize = iStream.Length
Response.ContentType = "video/mp4"
Response.AddHeader("Accept-Ranges", "bytes")
Response.AddHeader("Content-Range", "bytes 0-" + totalFileSize.ToString + "/" + totalFileSize.ToString)
Response.AddHeader("Content-Length", totalFileSize.ToString)
' Read the bytes.
While dataToRead > 0
' Verify that the client is connected.
If Response.IsClientConnected Then
' Read the data in buffer
length = iStream.Read(buffer, 0, 10000)
' Write the data to the current output stream.
Response.OutputStream.Write(buffer, 0, length)
' Flush the data to the HTML output.
Response.Flush()
ReDim buffer(10000) ' Clear the buffer
dataToRead = dataToRead - length
Else
isPartialFile = True
'record the data read in the database HERE (partial file)
'totalDelivered = totalFileSize - dataToRead
'prevent infinite loop if user disconnects
dataToRead = -1
End If
End While
iStream.Close()
Response.End()
How do we modify the above code to make it work with IOS devices assuming that the issue is with the 206 response header?