(VB.NET UWP/WinRT) REST Download Bandwidth Throttle

Demonstrates how to use download bandwidth throttling with the REST API. This example will download a file from Drobox using a file stream, with a limit on the bandwidth that can be used for the transfer.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' A Dropbox access token should have been previously obtained.
' Dropbox access tokens do not expire.
' See Dropbox Access Token.


' To use bandwidth throttling, the connection should be made using the socket API.
' This provides numerous properties to customize the connection, such as
' BandwidthThrottleDown, BandwidthThrottleUp, ClientIpAddress, ClintPort, Http Proxy,
' KeepAlive, PreferIpv6, RequireSslCertVerify, SoRcvBuf, SoSndBuf, SoReuseAddr,
' SOCKS proxy, TcpNoSDelay, TlsPinSet, TlsCipherSuite, SslAllowedCiphers, etc.

Dim socket As New Chilkat.Socket
Dim maxWaitMs As Integer = 5000
Dim success As Boolean = Await socket.ConnectAsync("content.dropboxapi.com",443,True,maxWaitMs)
If (success <> True) Then
    Debug.WriteLine(socket.LastErrorText)
    Debug.WriteLine("Connect Fail Reason: " & socket.ConnectFailReason)
    Exit Sub
End If


' Set the download bandwidth throttle rate to 50000 bytes per second.
socket.BandwidthThrottleDown = 50000

Dim rest As New Chilkat.Rest

' Tell the REST object to use the connected socket.
rest.UseConnection(socket,True)

' The remainder of this example is identical to the example at:
' Dropbox Download File.


' Add request headers.
rest.AddHeader("Authorization","Bearer DROPBOX_ACCESS_TOKEN")

' The download "parameters" are contained in JSON passed in an HTTP request header.
' This is the JSON indicating the file to be downloaded:
' { 
'    "path": "/Homework/lit/hamlet.xml",
' }


Dim json As New Chilkat.JsonObject
json.AppendString("path","/Homework/lit/hamlet.xml")
rest.AddHeader("Dropbox-API-Arg",json.Emit())

' Setup a file stream for the download
Dim fileStream As New Chilkat.Stream
fileStream.SinkFile = "qa_output/hamletFromDropbox.xml"

' Indicate that the call to FullRequestNoBody should send the response body
' to fileStream if the response status code is 200.
' If a non-success response status code is received, then nothing
' is streamed to the output file and the error response is returned by FullRequestNoBody.
Dim expectedStatus As Integer = 200
rest.SetResponseBodyStream(expectedStatus,True,fileStream)

Dim responseStr As String = Await rest.FullRequestNoBodyAsync("POST","/2/files/download")
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' When successful, Dropbox responds with a 200 response code.
If (rest.ResponseStatusCode <> 200) Then
    ' Examine the request/response to see what happened.
    Debug.WriteLine("response status code = " & rest.ResponseStatusCode)
    Debug.WriteLine("response status text = " & rest.ResponseStatusText)
    Debug.WriteLine("response header: " & rest.ResponseHeader)
    Debug.WriteLine("response body (if any): " & responseStr)
    Debug.WriteLine("---")
    Debug.WriteLine("LastRequestStartLine: " & rest.LastRequestStartLine)
    Debug.WriteLine("LastRequestHeader: " & rest.LastRequestHeader)
    Exit Sub
End If


' Information about the downloaded file is also available as JSON in a response header.
' The "dropbox-api-result" response header contains the information.  For example:
Dim apiResult As String = rest.ResponseHdrByName("dropbox-api-result")
Debug.WriteLine(apiResult)

' In this case, the pretty-formatted dropbox-api-result JSON looks like this:
' { 
'   "name": "hamlet.xml",
'   "path_lower": "/homework/lit/hamlet.xml",
'   "path_display": "/Homework/lit/hamlet.xml",
'   "id": "id:74FkdeNuyKAAAAAAAAAAAQ",
'   "client_modified": "2016-06-02T23:19:00Z",
'   "server_modified": "2016-06-02T23:19:00Z",
'   "rev": "9482db15f",
'   "size": 279658
' }

' Load the JSON, pretty-print it, and demonstrate how to get some values...
Dim jsonResult As New Chilkat.JsonObject
jsonResult.EmitCompact = False
jsonResult.Load(apiResult)
' Show the JSON pretty-printed...
Debug.WriteLine(jsonResult.Emit())

' Sample code to get data from the JSON response:
Dim size As Integer = jsonResult.IntOf("size")
Debug.WriteLine("size = " & size)

Dim rev As String = jsonResult.StringOf("rev")
Debug.WriteLine("rev = " & rev)

Dim clientModified As String = jsonResult.StringOf("client_modified")
Dim ckdt As New Chilkat.CkDateTime
ckdt.SetFromTimestamp(clientModified)
Dim bLocalTime As Boolean = True
Dim dt As Chilkat.DtObj = ckdt.GetDtObj(bLocalTime)
Debug.WriteLine(dt.Day & "/" & dt.Month & "/" & dt.Year & " " & dt.Hour & ":" & dt.Minute)