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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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Local $bSuccess = False

;  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.

$oTunnel = ObjCreate("Chilkat.SshTunnel")

;  The fixed destination that accepted connections are forwarded to.
$oTunnel.DestHostname = "db.internal.example.com"
$oTunnel.DestPort = 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).
$oTunnel.ListenBindIpAddress = "127.0.0.1"

Local $iSshPort = 22
$bSuccess = $oTunnel.Connect("ssh.example.com",$iSshPort)
If ($bSuccess = False) Then
    ConsoleWrite($oTunnel.LastErrorText & @CRLF)
    Exit
EndIf

;  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.
Local $sPassword = "mySshPassword"

$bSuccess = $oTunnel.AuthenticatePw("mySshLogin",$sPassword)
If ($bSuccess = False) Then
    ConsoleWrite($oTunnel.LastErrorText & @CRLF)
    Exit
EndIf

;  Pass 0 to let the operating system choose an available port.  After BeginAccepting succeeds,
;  ListenPort contains the actual port that was bound.
$bSuccess = $oTunnel.BeginAccepting(0)
If ($bSuccess = False) Then
    ConsoleWrite($oTunnel.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("Listening on 127.0.0.1 port " & $oTunnel.ListenPort & @CRLF)

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

Local $bWaitForThreadExit = True
$bSuccess = $oTunnel.CloseTunnel($bWaitForThreadExit)
If ($bSuccess = False) Then
    ConsoleWrite($oTunnel.LastErrorText & @CRLF)
    Exit
EndIf