(VB.NET) Asynchronous Sockets - Reading/Writing Data

Demonstrates the following using async methods:

Demonstrates receiving text on a socket connection up to and including when an expected CRLF arrives. The example sends an HTTP HEAD request to an HTTP server and then reads the response header using ReceiveToCRLF and ReceiveUntilMatch.

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

Dim socket As New Chilkat.Socket

' Connect using TLS to www.chilkatsoft.com
' We could also use a normal TCP connection also by specifying port 80 with useTls = False.
Dim useTls As Boolean = True
Dim maxWaitMillisec As Integer = 20000
Dim connectTask As Chilkat.Task = socket.ConnectAsync("www.chilkatsoft.com",443,useTls,maxWaitMillisec)
If (socket.LastMethodSuccess <> True) Then
    Debug.WriteLine(socket.LastErrorText)
    Exit Sub
End If


' Schedule the task for running on the thread pool.  This changes the task's state
' from Inert to Live.
Dim success As Boolean = connectTask.Run()
If (success <> True) Then
    Debug.WriteLine(connectTask.LastErrorText)

    Exit Sub
End If


' The application is now free to do anything else.
' For programming languages where Chilkat supports events, a TaskCompleted
' event will fire when the task is completed.

' For this example, we'll simply sleep and periodically
' check to see when the connection is ready.
While connectTask.Finished <> True

    ' Sleep 10 ms.
    connectTask.SleepMs(10)

End While

' A finished task could be one that was canceled, aborted, or truly finished.  

' If the task was "canceled", it was canceled prior to actually starting.  This could
' happen if the task was canceled while waiting in a thread pool queue to be scheduled by Chilkat's
' background thread pool scheduler.  

' If the task was "aborted", it indicates that it was canceled while running in a background thread.  
' The ResultErrorText will likely indicate that the task was aborted.

' If the task "completed", then it ran to completion, but the actual success/failure of the method
' is determined by the result obtained via a GetResult* method.  (A "completed" task will
' have a StatusInt equal to 7.   If the task finished, but was not completed, then it must've
' been aborted or canceled:
If (connectTask.StatusInt <> 7) Then
    Debug.WriteLine("Task did not complete.")
    Debug.WriteLine("task status: " & connectTask.Status)

    Exit Sub
End If

Dim connectSuccess As Boolean = connectTask.GetResultBool()
If (connectSuccess <> True) Then
    Debug.WriteLine("Connect failed.")
    Debug.WriteLine(connectTask.ResultErrorText)

    Exit Sub
End If





' Tell the socket object that all text is to be sent in the utf-8 encoding,
' and the text received is assumed to be utf-8.
socket.StringCharset = "utf-8"

' Send an HTTP HEAD request:
Dim sendTask As Chilkat.Task = socket.SendStringAsync("HEAD / HTTP/1.1" & vbCrLf & "Host: www.chilkatsoft.com" & vbCrLf & vbCrLf)
If (socket.LastMethodSuccess <> True) Then
    Debug.WriteLine(socket.LastErrorText)
    Exit Sub
End If

success = sendTask.Run()
If (success <> True) Then
    Debug.WriteLine(sendTask.LastErrorText)

    Exit Sub
End If

' The application is now free to do anything else.
' For programming languages where Chilkat supports events, 
' a TaskCompleted event will fire when the task is completed.
' This example will simply wait until the task completes...
While sendTask.Finished <> True
    ' Sleep 10 ms.
    sendTask.SleepMs(10)
End While
If (sendTask.StatusInt <> 7) Then
    Debug.WriteLine("Task did not complete.")
    Debug.WriteLine("task status: " & sendTask.Status)

    Exit Sub
End If

Dim sendSuccess As Boolean = sendTask.GetResultBool()
If (sendSuccess <> True) Then
    Debug.WriteLine("Send failed.")
    Debug.WriteLine(sendTask.ResultErrorText)

    Exit Sub
End If




' Wait a maximum of 4 seconds while no data is forthcoming:
socket.MaxReadIdleMs = 4000

' To explain MaxReadIdleMs further:  In Chilkat, a max "idle timeout" is the max time to wait
' while no additional data arrives on the socket.  Imagine if 10MB of data will be received
' where the 1st CRLF occurs at the very end.  As long as the data continues arriving and does not
' halt for more than 4000ms, then the ReceiveToCRLF will continue receiving.  It is only after
' the connection becomes idle for more than 4000ms that the app will giveup and fail the read.

' Get the 1st response line, which should be "HTTP/1.1 200 OK"
Dim receiveTask As Chilkat.Task = socket.ReceiveToCRLFAsync()
If (socket.LastMethodSuccess <> True) Then
    Debug.WriteLine(socket.LastErrorText)
    Exit Sub
End If

success = receiveTask.Run()
If (success <> True) Then
    Debug.WriteLine(receiveTask.LastErrorText)

    Exit Sub
End If

' The application is now free to do anything else.
' For programming languages where Chilkat supports events, 
' a TaskCompleted event will fire when the task is completed.
' This example will simply wait until the task completes...
While receiveTask.Finished <> True
    ' Sleep 10 ms.
    receiveTask.SleepMs(10)
End While
If (receiveTask.StatusInt <> 7) Then
    Debug.WriteLine("Task did not complete.")
    Debug.WriteLine("task status: " & receiveTask.Status)

    Exit Sub
End If

Dim responseStatusLine As String = receiveTask.GetResultString()

Debug.WriteLine("StatusLine: " & responseStatusLine)


' Now get the 1st line of the response header:
Dim responseHeaderLine As String = socket.ReceiveToCRLF()
If (socket.LastMethodSuccess <> True) Then
    Debug.WriteLine(socket.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("HeaderLine: " & responseHeaderLine)

' Now read the remainder of the response header by reading until a double CRLF is seen:
receiveTask = socket.ReceiveUntilMatchAsync(vbCrLf & vbCrLf)
If (socket.LastMethodSuccess <> True) Then
    Debug.WriteLine(socket.LastErrorText)
    Exit Sub
End If

success = receiveTask.Run()
If (success <> True) Then
    Debug.WriteLine(receiveTask.LastErrorText)

    Exit Sub
End If

' The application is now free to do anything else.
' For programming languages where Chilkat supports events, 
' a TaskCompleted event will fire when the task is completed.
' This example will simply wait until the task completes...
While receiveTask.Finished <> True
    ' Sleep 10 ms.
    receiveTask.SleepMs(10)
End While
If (receiveTask.StatusInt <> 7) Then
    Debug.WriteLine("Task did not complete.")
    Debug.WriteLine("task status: " & receiveTask.Status)

    Exit Sub
End If

Dim remainderOfHeader As String = receiveTask.GetResultString()

Debug.WriteLine("Remainder: " & remainderOfHeader)



' Close the connection with the server
' Wait a max of 20 seconds (20000 millsec)
success = socket.Close(20000)