(VB.NET) FTP through SSH Tunnel with Dynamic Port Forwarding

Demonstrates how to start a background thread that runs a portable SSH tunnel w/ dynamic port forwarding that the foreground thread can be used for establishing FTP sessions through an SSH tunnel.

Note: Some developers may be accustomed to starting an stunnel.exe proxy from https://www.stunnel.org. The stunnel.exe is not necessary here. Chilkat's background thread fulfills the task of what the external stunnel.exe does. Therefore, your application is self-contained, meaning that it can run anywhere because the SSH tunnel proxy is built-in.

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' Starting in v9.5.0.49, all Chilkat classes can be unlocked at once at the beginning of a program
' by calling UnlockBundle.  It requires a Bundle unlock code.
Dim chilkatGlob As New Chilkat.Global
Dim success As Boolean = chilkatGlob.UnlockBundle("Anything for 30-day trial.")
If (success <> True) Then
    Debug.WriteLine(chilkatGlob.LastErrorText)
    Exit Sub
End If


' This example requires Chilkat version 9.5.0.50 or greater.
Dim tunnel As New Chilkat.SshTunnel


Dim sshHostname As String = "sftp.example.com"
Dim sshPort As Integer = 22

' Connect to an SSH server and establish the SSH tunnel:
success = tunnel.Connect(sshHostname,sshPort)
If (success <> True) Then
    Debug.WriteLine(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.AuthenticatePw("mySshLogin","mySshPassword")
If (success <> True) Then
    Debug.WriteLine(tunnel.LastErrorText)
    Exit Sub
End If



' Indicate that the background SSH tunnel thread will behave as a SOCKS proxy server
' with dynamic port forwarding:
tunnel.DynamicPortForwarding = True

' We may optionally require that connecting clients authenticate with our SOCKS proxy server.
' To do this, set an inbound username/password.  Any connecting clients would be required to 
' use SOCKS5 with the correct username/password.
' If no inbound username/password is set, then our SOCKS proxy server will accept both
' SOCKS4 and SOCKS5 unauthenticated connections.

tunnel.InboundSocksUsername = "chilkat123"
tunnel.InboundSocksPassword = "password123"

' Start the listen/accept thread to begin accepting SOCKS proxy client connections.
' Listen on port 1080.
success = tunnel.BeginAccepting(1080)
If (success <> True) Then
    Debug.WriteLine(tunnel.LastErrorText)
    Exit Sub
End If



' Now that a background thread is running a SOCKS proxy server that forwards connections
' through an SSH tunnel, it is possible to use any Chilkat implemented protocol that is SOCKS capable,
' such as HTTP, POP3, SMTP, IMAP, FTP, etc.  The protocol may use SSL/TLS because the SSL/TLS
' will be passed through the SSH tunnel to the end-destination.  Also, any number of simultaneous
' connections may be routed through the SSH tunnel.


Dim ftp As New Chilkat.Ftp2

' Indicate that the HTTP object is to use our portable SOCKS proxy/SSH tunnel running in our background thread.
ftp.SocksHostname = "localhost"
' The SocksPort must equal the port passed to BeginAccepting above.
ftp.SocksPort = 1080
ftp.SocksVersion = 5
' The SOCKS5 login/password set here must equal the InboundSocksUsername/Password set above.
ftp.SocksUsername = "chilkat123"
ftp.SocksPassword = "password123"

' This is the actual FTP server domain or IP address, and the login/password for the user account on the destination FTP server.
ftp.Hostname = "ftp.someFtpServer.com"
ftp.Username = "myLogin"
ftp.Password = "myPassword"
ftp.AuthTls = True

' Connect and login (via the SSH tunnel) to the FTP server.
success = ftp.Connect()
If (success <> True) Then
    Debug.WriteLine(ftp.LastErrorText)
    Exit Sub
End If


' Change to the remote directory where the file is located.
' This step is only necessary if the file is not in the root directory
' for the FTP account.
success = ftp.ChangeRemoteDir("junk")
If (success <> True) Then
    Debug.WriteLine(ftp.LastErrorText)
    Exit Sub
End If


Dim localFilename As String = "c:/temp/hamlet.xml"
Dim remoteFilename As String = "hamlet.xml"


' Download a file.  (the data connection is also automatically established through the 
' SSH tunnel using dynamic port forwarding..)
success = ftp.GetFile(remoteFilename,localFilename)
If (success <> True) Then
    Debug.WriteLine(ftp.LastErrorText)
    Exit Sub
End If


' The disconnect is disconnecting with the FTP server and closes the SSH tunnel.
' The background tunnel thread is still running, and may be used for subsequent FTP connections,
' or even connections for any other purpose, such as HTTP, IMAP, SMTP, POP3, etc.
success = ftp.Disconnect()





' When the app is finished with the tunnel, it can cleanup..

' Stop the background listen/accept thread:
Dim waitForThreadExit As Boolean = True
success = tunnel.StopAccepting(waitForThreadExit)
If (success <> True) Then
    Debug.WriteLine(tunnel.LastErrorText)
    Exit Sub
End If



' Close the SSH tunnel (would also kick any remaining connected clients).
success = tunnel.CloseTunnel(waitForThreadExit)
If (success <> True) Then
    Debug.WriteLine(tunnel.LastErrorText)
    Exit Sub
End If