SQL Server

Start an SSH Tunnel Listener (BeginAccepting)

Demonstrates the Chilkat SshTunnel.BeginAccepting method, which creates and starts the local listener on the given port. The only argument is the listen port. Connect and authenticate first — clients accepted before authentication cannot be forwarded. The IsAccepting property reports whether the listener is running.

Background: This is the step that actually turns the object into a working tunnel: it spawns a background thread that accepts local TCP connections and forwards each through the authenticated SSH transport. Because the forwarding runs on its own thread, control returns to your program immediately and the tunnel operates while the rest of the application does other work — which is why a separate CloseTunnel is needed to shut it down cleanly.

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-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    --  Demonstrates the SshTunnel.BeginAccepting method, which creates and starts the local listener
    --  on the given port.  The only argument is the listen port.  Connect and authenticate first;
    --  clients accepted before authentication cannot be forwarded.

    DECLARE @tunnel int
    EXEC @hr = sp_OACreate 'Chilkat.SshTunnel', @tunnel OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    EXEC sp_OASetProperty @tunnel, 'DestHostname', 'db.internal.example.com'
    EXEC sp_OASetProperty @tunnel, 'DestPort', 5432

    DECLARE @sshPort int
    SELECT @sshPort = 22
    EXEC sp_OAMethod @tunnel, 'Connect', @success OUT, 'ssh.example.com', @sshPort
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @tunnel, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @tunnel
        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.
    DECLARE @password nvarchar(4000)
    SELECT @password = 'mySshPassword'

    EXEC sp_OAMethod @tunnel, 'AuthenticatePw', @success OUT, 'mySshLogin', @password
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @tunnel, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @tunnel
        RETURN
      END

    --  Start the local listener.  Local TCP connections to this port are forwarded to DestHostname:DestPort
    --  through the SSH server.
    DECLARE @listenPort int
    SELECT @listenPort = 1080
    EXEC sp_OAMethod @tunnel, 'BeginAccepting', @success OUT, @listenPort
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @tunnel, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @tunnel
        RETURN
      END

    --  IsAccepting reports whether the listener thread is running.
    EXEC sp_OAGetProperty @tunnel, 'IsAccepting', @iTmp0 OUT
    IF @iTmp0
      BEGIN

        PRINT 'The tunnel is accepting connections on port ' + @listenPort
      END

    --  ... the tunnel forwards traffic on a background thread while your application runs ...

    DECLARE @waitForThreadExit int
    SELECT @waitForThreadExit = 1
    EXEC sp_OAMethod @tunnel, 'CloseTunnel', @success OUT, @waitForThreadExit
    IF @success = 0
      BEGIN
        EXEC sp_OAGetProperty @tunnel, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @tunnel
        RETURN
      END

    EXEC @hr = sp_OADestroy @tunnel


END
GO