PureBasic

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.

PureBasic

IncludeFile "CkSshTunnel.pb"
IncludeFile "CkFtp2.pb"

Procedure ChilkatExample()

    success.i = 0

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

    success = 0

    tunnel.i = CkSshTunnel::ckCreate()
    If tunnel.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    sshHostname.s = "sftp.example.com"
    sshPort.i = 22

    ; Connect to an SSH server and establish the SSH tunnel:
    success = CkSshTunnel::ckConnect(tunnel,sshHostname,sshPort)
    If success <> 1
        Debug CkSshTunnel::ckLastErrorText(tunnel)
        CkSshTunnel::ckDispose(tunnel)
        ProcedureReturn
    EndIf

    ; Authenticate with the SSH server via a login/password
    ; or with a public key.  
    ; This example demonstrates SSH password authentication.
    success = CkSshTunnel::ckAuthenticatePw(tunnel,"mySshLogin","mySshPassword")
    If success <> 1
        Debug CkSshTunnel::ckLastErrorText(tunnel)
        CkSshTunnel::ckDispose(tunnel)
        ProcedureReturn
    EndIf

    ; Indicate that the background SSH tunnel thread will behave as a SOCKS proxy server
    ; with dynamic port forwarding:
    CkSshTunnel::setCkDynamicPortForwarding(tunnel, 1)

    ; 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.

    CkSshTunnel::setCkInboundSocksUsername(tunnel, "chilkat123")
    CkSshTunnel::setCkInboundSocksPassword(tunnel, "password123")

    ; Start the listen/accept thread to begin accepting SOCKS proxy client connections.
    ; Listen on port 1080.
    success = CkSshTunnel::ckBeginAccepting(tunnel,1080)
    If success <> 1
        Debug CkSshTunnel::ckLastErrorText(tunnel)
        CkSshTunnel::ckDispose(tunnel)
        ProcedureReturn
    EndIf

    ; 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.

    ftp.i = CkFtp2::ckCreate()
    If ftp.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Indicate that the HTTP object is to use our portable SOCKS proxy/SSH tunnel running in our background thread.
    CkFtp2::setCkSocksHostname(ftp, "localhost")
    ; The SocksPort must equal the port passed to BeginAccepting above.
    CkFtp2::setCkSocksPort(ftp, 1080)
    CkFtp2::setCkSocksVersion(ftp, 5)
    ; The SOCKS5 login/password set here must equal the InboundSocksUsername/Password set above.
    CkFtp2::setCkSocksUsername(ftp, "chilkat123")
    CkFtp2::setCkSocksPassword(ftp, "password123")

    ; This is the actual FTP server domain or IP address, and the login/password for the user account on the destination FTP server.
    CkFtp2::setCkHostname(ftp, "ftp.someFtpServer.com")
    CkFtp2::setCkUsername(ftp, "myLogin")
    CkFtp2::setCkPassword(ftp, "myPassword")
    CkFtp2::setCkAuthTls(ftp, 1)

    ; Connect and login (via the SSH tunnel) to the FTP server.
    success = CkFtp2::ckConnect(ftp)
    If success <> 1
        Debug CkFtp2::ckLastErrorText(ftp)
        CkSshTunnel::ckDispose(tunnel)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf

    ; 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 = CkFtp2::ckChangeRemoteDir(ftp,"junk")
    If success <> 1
        Debug CkFtp2::ckLastErrorText(ftp)
        CkSshTunnel::ckDispose(tunnel)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf

    localFilename.s = "c:/temp/hamlet.xml"
    remoteFilename.s = "hamlet.xml"

    ; Download a file.  (the data connection is also automatically established through the 
    ; SSH tunnel using dynamic port forwarding..)
    success = CkFtp2::ckGetFile(ftp,remoteFilename,localFilename)
    If success <> 1
        Debug CkFtp2::ckLastErrorText(ftp)
        CkSshTunnel::ckDispose(tunnel)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf

    ; 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 = CkFtp2::ckDisconnect(ftp)

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

    ; Stop the background listen/accept thread:
    waitForThreadExit.i = 1
    success = CkSshTunnel::ckStopAccepting(tunnel,waitForThreadExit)
    If success <> 1
        Debug CkSshTunnel::ckLastErrorText(tunnel)
        CkSshTunnel::ckDispose(tunnel)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf

    ; Close the SSH tunnel (would also kick any remaining connected clients).
    success = CkSshTunnel::ckCloseTunnel(tunnel,waitForThreadExit)
    If success <> 1
        Debug CkSshTunnel::ckLastErrorText(tunnel)
        CkSshTunnel::ckDispose(tunnel)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf



    CkSshTunnel::ckDispose(tunnel)
    CkFtp2::ckDispose(ftp)


    ProcedureReturn
EndProcedure