Pascal (Lazarus/Delphi)

Abort a Running SSH Tunnel Operation

Demonstrates the AbortCurrent property, which requests that the currently running foreground operation be aborted. It is intended to be set to true from another thread — for example, to interrupt a synchronous Connect that is waiting for an unresponsive server.

Background: A synchronous call like Connect blocks the calling thread until it finishes or times out, which is a problem when a user clicks "Cancel" or the app needs to shut down. Setting AbortCurrent from a different thread breaks the blocked operation out early, returning a failure the caller can handle. Note its scope is deliberately limited to the current foreground operation: it does not stop the background listener or terminate established tunnel clients — use StopAccepting or CloseTunnel for those.

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Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.SshTunnel;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  tunnel: TSshTunnel;
  sshPort: Integer;
  waitForThreadExit: Boolean;

begin
  success := False;

  //  Demonstrates the SshTunnel.AbortCurrent property, which requests that the currently running
  //  foreground operation be aborted.

  tunnel := TSshTunnel.Create;

  //  AbortCurrent is intended to be set to True from ANOTHER thread to interrupt a synchronous
  //  operation in progress -- for example, a Connect that is waiting for an unresponsive server.
  //  It does not stop the background listener or terminate established background tunnel clients.
  //  
  //  The assignment below illustrates the property.  In a real application it would be set on a
  //  separate thread while Connect blocks; if it becomes True, the blocked Connect returns with a
  //  failure.
  tunnel.AbortCurrent := False;

  tunnel.DestHostname := 'db.internal.example.com';
  tunnel.DestPort := 5432;

  sshPort := 22;
  success := tunnel.Connect('ssh.example.com',sshPort);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;
  WriteLn('Connected.');

  waitForThreadExit := True;
  success := tunnel.CloseTunnel(waitForThreadExit);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;


  tunnel.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.