(Visual Basic 6.0) TLS Connection within SSH Tunnel (Port Forwarding)

Demonstrates using Chilkat Socket to communicate to a TLS service through an SSH tunnel. This example will connect (through a port-forwarded SSH tunnel) to the GMAIL IMAP server via TLS and will receive the greeting.

Note: The Chilkat IMAP API provides direct support for using SSH tunneling with the IMAP protocol. This example serves only to demonstrate that, in general, TLS connections can be tunneled through SSH.

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

Dim tunnel As New ChilkatSocket

Dim sshHostname As String
sshHostname = "www.my-ssh-server.com"
Dim sshPort As Long
sshPort = 22

' Connect to an SSH server and establish the SSH tunnel:
Dim success As Long
success = tunnel.SshOpenTunnel(sshHostname,sshPort)
If (success <> 1) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

' Authenticate with the SSH server via a login/password
' or with a public key.
' This example demonstrates SSH password authentication.
success = tunnel.SshAuthenticatePw("mySshLogin","mySshPassword")
If (success <> 1) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

'  OK, the SSH tunnel is setup.  Now open a channel within the tunnel.
'  Once the channel is obtained, the Socket API may
'  be used exactly the same as usual, except all communications
'  are sent through the channel in the SSH tunnel.
'  Any number of channels may be created from the same SSH tunnel.
'  Multiple channels may coexist at the same time.

' Connect to the GMAIL IMAP server via TLS (through the port-forwarded SSH tunnel)
Dim channel As ChilkatSocket
Dim maxWaitMs As Long
maxWaitMs = 4000
Dim useTls As Long
useTls = 1
Set channel = tunnel.SshOpenChannel("imap.gmail.com",993,useTls,maxWaitMs)
If (tunnel.LastMethodSuccess = 0) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

' If desired, visually inspect the LastErrorText to see that indeed the TLS
' protocol was run inside the SSH tunnel:
Debug.Print tunnel.LastErrorText

' The first thing an IMAP server does is to send a greeting terminated with a CRLF.
Dim imapGreeting As String
imapGreeting = channel.ReceiveToCRLF()
If (channel.LastMethodSuccess <> 1) Then
    Debug.Print channel.LastErrorText

    Exit Sub
End If

Debug.Print imapGreeting

' Close the connection to imap.gmail.com.  This is actually closing our channel
' within the SSH tunnel, but keeps the tunnel open for the next port-forwarded connection.
success = channel.Close(maxWaitMs)
If (success <> 1) Then
    Debug.Print channel.LastErrorText
    Exit Sub
End If

' Finally, close the SSH tunnel.
success = tunnel.SshCloseTunnel()
If (success <> 1) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

Debug.Print "TLS SSH tunneling example completed."