Visual Basic 6.0

Socket Convert Existing TCP Connection to SSL/TLS

Demonstrates the Chilkat Socket ConvertToSsl method. Visual Basic 6.0

Dim success As Long
success = 0

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

Dim sock As New ChilkatSocket

' --------------------------------------------------------------------
' This example uses the public TCP/TLS echo service at https://tcpbin.com/
' --------------------------------------------------------------------

' The echo server at tcpbin.com expects to receive TCP connections on port 4242, and TLS connections on port 4243.
' We could simply connect to port 4243 using TLS like this.
' However, further below, this example shows how to initially make a TCP connection, and then convert the connection to TLS.
Dim useTls As Long
useTls = 1
Dim port As Long
port = 4243
Dim maxWaitMs As Long
maxWaitMs = 5000
success = sock.Connect("tcpbin.com",port,useTls,maxWaitMs)
If (success = 0) Then
    Debug.Print sock.LastErrorText
    Exit Sub
End If

' OK, we have a TLS connection.
' Note: The server chooses the TLS protocol version. 
' We can see the version of the TLS connection that was established:
Debug.Print "TLS version: " & sock.TlsVersion

success = sock.Close(maxWaitMs)

' ---------------------------------------------------------------------
' Now we'll do the same, except first we connect to port 4243 using TCP,
' and then convert the connection to TLS.
' 
' This may seem pointless, and it is for the case w/ this server.  However, there could be situations
' where you're interacting with a server of some kind where there is a need to convert to/from TLS.
' (This is common internal to many protocols, such as SMTP, IMAP, FTP, etc., and it is often called "explicit" SSL/TLS)

' Connect again, except this time useTls is 0, so we only have a simple TCP connection after this call.
useTls = 0
success = sock.Connect("tcpbin.com",port,useTls,maxWaitMs)
If (success = 0) Then
    Debug.Print sock.LastErrorText
    Exit Sub
End If

' Convert the existing TCP connection to TLS.
' (The method name uses "SSL" because long ago, at the time of initial development, TLS 1.0 did not yet exist.)
success = sock.ConvertToSsl()
If (success = 0) Then
    Debug.Print sock.LastErrorText
    Exit Sub
End If

' OK, we now have a TLS connection.
' Again, we can see the TLS version:
Debug.Print "TLS version: " & sock.TlsVersion

success = sock.Close(maxWaitMs)