DataFlex

SSH Tunnel Static (Fixed-Destination) Port Forwarding

Demonstrates fixed-destination port forwarding with the DestHostname, DestPort, ListenBindIpAddress, and ListenPort properties. Every local connection accepted by the listener is forwarded to the same fixed destination through the SSH server.

Background: This is the classic ssh -L scenario: expose a single remote service — a database, an internal web app — at a local port. Binding the listener to 127.0.0.1 keeps the tunnel private to the local machine, whereas 0.0.0.0 would let other hosts route through it. Passing 0 to BeginAccepting lets the OS pick a free port, which ListenPort then reports — handy when a fixed port might already be in use.

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Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoTunnel
    Integer iSshPort
    String sPassword
    Boolean iWaitForThreadExit
    String sTemp1
    Integer iTemp1

    Move False To iSuccess

    //  Demonstrates fixed-destination (static) port forwarding with the SshTunnel properties
    //  DestHostname, DestPort, ListenBindIpAddress, and ListenPort.
    //  
    //  Every local connection accepted by the listener is forwarded to the same fixed destination
    //  through the SSH server.

    Get Create (RefClass(cComChilkatSshTunnel)) To hoTunnel
    If (Not(IsComObjectCreated(hoTunnel))) Begin
        Send CreateComObject of hoTunnel
    End

    //  The fixed destination that accepted connections are forwarded to.
    Set ComDestHostname Of hoTunnel To "db.internal.example.com"
    Set ComDestPort Of hoTunnel To 5432

    //  Bind the listener to loopback so only local processes can use the tunnel.  Use "0.0.0.0" to
    //  accept connections from other machines (less secure).
    Set ComListenBindIpAddress Of hoTunnel To "127.0.0.1"

    Move 22 To iSshPort
    Get ComConnect Of hoTunnel "ssh.example.com" iSshPort To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  Normally you would not hard-code the password in source.  You should instead obtain it
    //  from an interactive prompt, environment variable, or a secrets vault.
    Move "mySshPassword" To sPassword

    Get ComAuthenticatePw Of hoTunnel "mySshLogin" sPassword To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  Pass 0 to let the operating system choose an available port.  After BeginAccepting succeeds,
    //  ListenPort contains the actual port that was bound.
    Get ComBeginAccepting Of hoTunnel 0 To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComListenPort Of hoTunnel To iTemp1
    Showln "Listening on 127.0.0.1 port " iTemp1

    //  Applications now connect to 127.0.0.1:ListenPort as if it were the database server.

    Move True To iWaitForThreadExit
    Get ComCloseTunnel Of hoTunnel iWaitForThreadExit To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoTunnel To sTemp1
        Showln sTemp1
        Procedure_Return
    End



End_Procedure