Response.Redirect a download in progress - asp.net

Question

I have a website where a user can choose to view a video (no copyright) that is on a 3rd party website. From the moment the user choose it, it needs to be downloaded onto my web server before the user can access it. I tried to automatically start the download on the 3rd party website and make a response.redirect with this path, but when the user is watching the video, if the video has only 10 seconds downloaded, any player/browser will considere this video as a ten-seconds video and stop it after 10 seconds.
What would be the best practice to redirect a stream instead of a file?

Answer 1

I found that this piece of code is doing exactly what I want. It downloads a file on a third party website, and as it's streaming it, each chunk is writen in the Response so that it completely obsfuscates the origin. Thus, it is possible to serve any file from any website as if I own it.
Private Sub SendFile(ByVal url As String)
Dim stream As System.IO.Stream = Nothing
Dim bytesToRead As Integer = 10000
Dim buffer() As Byte = New Byte((bytesToRead) - 1) {}
Try
Dim fileReq As System.Net.WebRequest = CType(System.Net.HttpWebRequest.Create(url), System.Net.HttpWebRequest)
Dim fileResp As System.Net.HttpWebResponse = CType(fileReq.GetResponse, System.Net.HttpWebResponse)
If (fileReq.ContentLength > 0) Then
fileResp.ContentLength = fileReq.ContentLength
End If
stream = fileResp.GetResponseStream
Dim resp As System.Web.HttpResponse = HttpContext.Current.Response
resp.ContentType = "application/octet-stream"
resp.AddHeader("Content-Disposition", ("attachment; filename=\""" + ("mp3" + "\""")))
resp.AddHeader("Content-Length", fileResp.ContentLength.ToString)
Dim length As Integer = 1000000
While (length > 0)
If resp.IsClientConnected Then
length = stream.Read(buffer, 0, bytesToRead)
resp.OutputStream.Write(buffer, 0, length)
resp.Flush()
buffer = New Byte((bytesToRead) - 1) {}
Else
length = -1
End If
End While
Catch
stream.Close()
Finally
If (Not (stream) Is Nothing) Then
stream.Close()
End If
End Try
Response.End()
End Sub