Pascal (Lazarus/Delphi)

Socket Convert Existing TCP Connection to SSL/TLS

Demonstrates the Chilkat Socket ConvertToSsl method. 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.Socket;

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

procedure RunDemo;
var
  success: Boolean;
  sock: TSocket;
  useTls: Boolean;
  port: Integer;
  maxWaitMs: Integer;

begin
  success := False;

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

  sock := TSocket.Create;

  //  --------------------------------------------------------------------
  //  This example uses the public TCP/TLS echo service at https://tcpbin.com/
  //  --------------------------------------------------------------------

  //  The echo server at tcpbin.com expects to receive TCP connections on port 4242, and TLS connections on port 4243.
  //  We could simply connect to port 4243 using TLS like this.
  //  However, further below, this example shows how to initially make a TCP connection, and then convert the connection to TLS.
  useTls := True;
  port := 4243;
  maxWaitMs := 5000;
  success := sock.Connect('tcpbin.com',port,useTls,maxWaitMs);
  if (success = False) then
    begin
      WriteLn(sock.LastErrorText);
      Exit;
    end;

  //  OK, we have a TLS connection.
  //  Note: The server chooses the TLS protocol version. 
  //  We can see the version of the TLS connection that was established:
  WriteLn('TLS version: ' + sock.TlsVersion);

  sock.Close(maxWaitMs);

  //  ---------------------------------------------------------------------
  //  Now we'll do the same, except first we connect to port 4243 using TCP,
  //  and then convert the connection to TLS.
  //  
  //  This may seem pointless, and it is for the case w/ this server.  However, there could be situations
  //  where you're interacting with a server of some kind where there is a need to convert to/from TLS.
  //  (This is common internal to many protocols, such as SMTP, IMAP, FTP, etc., and it is often called "explicit" SSL/TLS)

  //  Connect again, except this time useTls is False, so we only have a simple TCP connection after this call.
  useTls := False;
  success := sock.Connect('tcpbin.com',port,useTls,maxWaitMs);
  if (success = False) then
    begin
      WriteLn(sock.LastErrorText);
      Exit;
    end;

  //  Convert the existing TCP connection to TLS.
  //  (The method name uses "SSL" because long ago, at the time of initial development, TLS 1.0 did not yet exist.)
  success := sock.ConvertToSsl();
  if (success = False) then
    begin
      WriteLn(sock.LastErrorText);
      Exit;
    end;

  //  OK, we now have a TLS connection.
  //  Again, we can see the TLS version:
  WriteLn('TLS version: ' + sock.TlsVersion);

  sock.Close(maxWaitMs);


  sock.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.