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(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.
' Starting in v188.8.131.52, 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 184.108.40.206 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
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