(Visual Basic 6.0) Accept TLS Connection with Client Authentication

Demonstrates how to accept a TLS connection requiring client authentication. This is the case where the TLS client sends a certificate. It is also known as "Two-Way SSL".

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 listenSslSocket As New ChilkatSocket

' An SSL/TLS server needs a digital certificate.  This example loads it from a PFX file.
' Note: This is the server's certificate.

Dim cert As New ChilkatCert
' The 1st argument is the file path, the 2nd arg is the 
' PFX file's password:
Dim success As Long
success = cert.LoadPfxFile("chilkat.pfx","test")
If (success <> 1) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

' To accept client client certificates in the TLS handshake,
' we must indicate a list of acceptable client certificate root CA DN's
' that are allowed.  (DN is an acronym for Distinguished Name.)
' Call AddSslAcceptableClientCaDn once for each acceptable CA DN.
' Here are a few examples so you can see the general format of a DN.
success = listenSslSocket.AddSslAcceptableClientCaDn("C=SE, O=AddTrust AB, OU=AddTrust External TTP Network, CN=AddTrust External CA Root")
success = listenSslSocket.AddSslAcceptableClientCaDn("O=Digital Signature Trust Co., CN=DST Root CA X3")

' Use the certificate:
success = listenSslSocket.InitSslServer(cert)
If (success <> 1) Then
    Debug.Print listenSslSocket.LastErrorText
    Exit Sub
End If

' Bind and listen on a port:
Dim myPort As Long
myPort = 8123
' Allow for a max of 5 queued connect requests.
Dim backLog As Long
backLog = 5
success = listenSslSocket.BindAndListen(myPort,backLog)
If (success <> 1) Then
    Debug.Print listenSslSocket.LastErrorText
    Exit Sub
End If

' If accepting an SSL/TLS connection, the SSL handshake is part of the connection
' establishment process. This involves a few back-and-forth messages between the 
' client and server to establish algorithms and a shared key to create the secure 
' channel. The sending and receiving of these messages are governed by the 
' MaxReadIdleMs and MaxSendIdleMs properties. If these properties are set to 0 
' (and this is the default unless changed by your application), then the 
' AcceptNextConnection can hang indefinitely during the SSL handshake process. 
' Make sure these properties are set to appropriate values before calling AcceptNextConnection.

' Set a 10 second max for waiting to read/write.  This is for the SSL/TLS handshake establishment.
listenSslSocket.MaxReadIdleMs = 10000
listenSslSocket.MaxSendIdleMs = 10000

' Accept a single client connection and establish the secure SSL/TLS channel:
Dim clientSock As ChilkatSocket
Dim maxWaitMillisec As Long
maxWaitMillisec = 20000
Set clientSock = listenSslSocket.AcceptNextConnection(maxWaitMillisec)
If (listenSslSocket.LastMethodSuccess = 0) Then
    Debug.Print listenSslSocket.LastErrorText
    Exit Sub
End If

' The client (in this example) is going to send a "Hello Server! -EOM-" 
' message.  Read it:
Dim receivedMsg As String
receivedMsg = clientSock.ReceiveUntilMatch("-EOM-")
If (clientSock.LastMethodSuccess <> 1) Then
    Debug.Print clientSock.LastErrorText
    Exit Sub
End If

Debug.Print receivedMsg

' Send a "Hello Client! -EOM-" message:
success = clientSock.SendString("Hello Client! -EOM-")
If (success <> 1) Then
    Debug.Print clientSock.LastErrorText
    Exit Sub
End If

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