HTTP in a Background Thread (Asynchronous HTTP)

This example shows the technique one would follow to run any Chilkat HTTP method in a background task. (Only HTTP methods that communicate with an HTTP server are background-enabled. Methods that perform no HTTP communications return immediately and never need to be backgrounded.)

Download Chilkat HTTP ActiveX

Dim http As New ChilkatHttp

Dim success As Long

'  Any string unlocks the component for the 1st 30-days.
success = http.UnlockComponent("Anything for 30-day trial")
If (success <> 1) Then
    MsgBox http.LastErrorText
    Exit Sub
End If

'  To run an HTTP method asynchronously in a background thread, set
'  the UseBgThread property equal to 1
http.UseBgThread = 1

'  For those programming languages that support event callbacks:
'  events are not fired when a task is running in the background thread.
'  Instead, Chilkat has added the "event log" mechanism.  While the
'  background task is running, events that normally would've been fired
'  are accumulated in the event log.  Your application may periodically check
'  the event log to keep track of the progress of the background task.
'  To enable event logging, set the KeepEventLog property = 1
http.KeepEventLog = 1

'  Start an asynchronous HTTP download in a background thread.
'  The method will return cktrue if the task was successfully started.
'  Note: When the UseBgThread property = 1, all methods involving
'  HTTP communications will be asynchronous.  These methods include:
'  SynchronousRequest, QuickGetStr, QuickGet, PostUrlEncoded, XmlRpc,
'  XmlRpcPut, QuickPutStr, QuickGetObj, QuickDeleteStr, PutText,
'  PutBinary, PostBinary, PostMime, GetHead, DownloadAppend, etc.
success = http.Download("http://www.chilkatsoft.com/download/ChilkatJava.zip","ChilkatJava.zip")
If (success <> 1) Then
    Text1.Text = Text1.Text & http.LastErrorText & vbCrLf
    Exit Sub
Else
    Text1.Text = Text1.Text & "Initiated asynchronous HTTP download..." & vbCrLf
End If

'  Write a loop to wait for the background task to complete.
'  Your application would typically do something different than this --
'  after all... there's no point in doing the task asynchronously if your application
'  is simply going to wait for it to complete -- that's the same as doing it synchronously,
'  and that could've been achieved by a single call to the http.Download method
'  with the UseBgThread = 0.
'  However... we do this here for the purpose of demonstration...
Do While (http.BgTaskRunning = 1)
    '  Show the events in the event log that have accumulated so far...
    Dim n As Long
    n = http.EventLogCount
    If (n > 0) Then
        Dim i As Long
        For i = 0 To n - 1
            Text1.Text = Text1.Text & http.EventLogName(i) _
                 & ": " & http.EventLogValue(i) & vbCrLf
        Next
        http.ClearEventLog 
    End If

    '  In some programming languages, you might wish to handle user-interface events
    '  For example, in C#  you might call Application.DoEvents()

    '  Sleep .1 seconds -- to keep the CPU from being 100% busy...
    http.SleepMs 100
Loop

'  Once the background task has completed, check it for success/failure:
If (http.BgTaskSuccess) Then
    Text1.Text = Text1.Text & "Background task completed successfully." & vbCrLf
End If