(Visual Basic 6.0) Bidirectional Sockets (TLS or non-TLS, simultaneous reading and writing a connection)

This example demonstrates how to simultaneously read/write on a single socket connection.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

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

Dim tlsRead As New ChilkatSocket

' We'll just use an HTTPS server for this example...
Dim bUseTls As Long
bUseTls = 1
Dim maxWaitMs As Long
maxWaitMs = 5000
Dim success As Long
success = tlsRead.Connect("www.chilkatsoft.com",443,bUseTls,maxWaitMs)
If (success <> 1) Then
    Debug.Print tlsRead.LastErrorText
    Exit Sub
End If

' Chilkat classes are thread-safe.  This means that only one method call can be active
' at a time for a given object instance.  It would seem that this would prevent the possibility
' to simultaneously read/write a given connection because it would require two method calls
' to be simultaneously active: one for reading and one for writing.
' 
' There's a trick to doing it...
' 
' The CloneSocket method is provided to get a new object instance that shares the same socket
' connection.  This allows for the coarse-grained object-level thread safety to be maintained, 
' while finer-grained thread-safety mechanisms keep things kosher internally.

' One object will be used for reading, and the cloned socket is used for writing.
' It doesn't matter which --  you can use the cloned socket for reading or the original for writing.
' However.. if you try to read simultneously from both the original and cloned objects at the same
' time, then one will block until the other finishes.  (This is because of the finer-grained thread
' safety internally.)  The same is true if you try to write both socket objects simultaneously.

Dim tlsWrite As ChilkatSocket
Set tlsWrite = tlsRead.CloneSocket()

' Let's start an async read on the socket.  Nothing will be arriving until we actually send the GET
' request and the server responds.  This will read until the end of the HTTP response header.
Dim task As ChilkatTask
Set task = tlsRead.ReceiveUntilMatchAsync(vbCrLf & vbCrLf)
success = task.Run()

' Now send the request.  This should not block because the read is happening on the tlsRead object.
Dim httpGetReq As String
httpGetReq = "GET / HTTP/1.1" & vbCrLf & "Host: www.chilkatsoft.com" & vbCrLf & vbCrLf
success = tlsWrite.SendString(httpGetReq)
' Assuming success for the example...

' Wait for the read task to finish.
' The 1/0 returned by Wait applies to the Wait method call, not the task.
maxWaitMs = 5000
success = task.Wait(maxWaitMs)
If (Not success Or (task.StatusInt <> 7) Or (task.TaskSuccess <> 1)) Then
    If (Not success) Then
        ' The task.LastErrorText applies to the Wait method call.
        Debug.Print task.LastErrorText
    Else
        ' The ResultErrorText applies to the underlying task method call (i.e. the Connect)
        Debug.Print task.Status
        Debug.Print task.ResultErrorText
    End If

    Exit Sub
End If

' Examine the received HTTP response header:
Debug.Print "HTTP response header:"
Debug.Print task.GetResultString()

' We should get a response that looks like this:
' 	HTTP response header:
' 	HTTP/1.1 200 OK
' 	Cache-Control: private
' 	Content-Length: 7477
' 	Content-Type: text/html
' 	Server: Microsoft-IIS/8.5
' 	Set-Cookie: ASPSESSIONIDSWDSTRTQ=BBNMIKGCHFJNILFFPLDIOGDE; secure; path=/
' 	X-Powered-By: ASP.NET
' 	X-Powered-By-Plesk: PleskWin
' 	Date: Thu, 06 Apr 2017 12:03:30 GMT

' Forget about the remainder of the HTTP response... The example was only to demonstrate
' simultaneous reading/writing..
maxWaitMs = 20
success = tlsRead.Close(maxWaitMs)