B4X

FTP through SSH Tunnel with Dynamic Port Forwarding

See more FTP Examples

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.

B4X

Dim success As Boolean = False

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

success = False

Dim tunnel As ChilkatSshTunnel
tunnel.Initialize("tunnel")

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

'  Connect to an SSH server and establish the SSH tunnel:
success = tunnel.Connect(sshHostname, sshPort)
If success <> True Then
    Log(tunnel.LastErrorText)
    Return
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
    Log(tunnel.LastErrorText)
    Return
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
    Log(tunnel.LastErrorText)
    Return
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 ChilkatFtp2
ftp.Initialize("ftp")

'  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
    Log(ftp.LastErrorText)
    Return
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
    Log(ftp.LastErrorText)
    Return
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
    Log(ftp.LastErrorText)
    Return
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
    Log(tunnel.LastErrorText)
    Return
End If


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