Pascal (Lazarus/Delphi)

Using IMAP IDLE to Wait for Updates

This example demonstrates how to use the IMAP IDLE functionality in Chilkat. 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.Imap;

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

procedure RunDemo;
var
  success: Boolean;
  imap: TImap;
  idleResultXml: string;

begin
  success := False;

  imap := TImap.Create;

  //  ....
  //  ....
  //  ....

  //  Select an IMAP mailbox
  success := imap.SelectMailbox('INBOX');
  if (success <> True) then
    begin
      WriteLn(imap.LastErrorText);
      Exit;
    end;

  //  After a mailbox has been selected, IDLE may begin.
  //  Idling tells the IMAP server to push unsolicited updates for the selected
  //  mailbox to the connected client (which is your application).
  success := imap.IdleStart();
  if (success <> True) then
    begin
      WriteLn(imap.LastErrorText);
      Exit;
    end;

  //  Once idling has started, your code still has to periodically check to see
  //  if any updates have arrived.  However, this is significantly different
  //  then what normally occurs when checking email.  The IdleCheck does NOT
  //  send a message to the IMAP server.  It simply checks the connection to see
  //  if any data has arrived.  If so, it can be consumed and the client (your app)
  //  can react appropriately.  

  //  Note: It is recommended that idling only run for a max of 20 minutes before stopping and
  //  re-starting the IDLE.  This is to maintain a minimum low level of activity so that 
  //  the IMAP server does not disconnect (which it may do if it considers the connection to 
  //  be truly inactive, i.e. forgotten).

  //  To check the connection for IDLE updates, call IdleCheck.  The 1st argument indicates how
  //  long we're willing to wait. We'll wait 1 millisecond:

  idleResultXml := imap.IdleCheck(1);
  if (imap.LastMethodSuccess <> True) then
    begin
      WriteLn(imap.LastErrorText);
      Exit;
    end;

  //  See the online reference documentation for details regarding the XML that is returned.
  //  Your application code would parse the XML to determine what action to take.
  //  If the XML contains "<idle></idle>", then no updates are available and your application
  //  would call IdleCheck again at some point in the future.

  //  If updates are available, the IDLE must be terminated by calling IdleDone, like this:
  success := imap.IdleDone();
  if (success <> True) then
    begin
      WriteLn(imap.LastErrorText);
      Exit;
    end;

  //  Once the IDLE is terminated, your application can make calls to fetch email, etc.
  //  Any attempt to communicate with the IMAP server prior to terminating the IDLE will
  //  result in failure.

  //  IMPORTANT: Please realize that your application code will be structured differently than shown here.
  //  The call to IdleCheck will likely be in a function/procedure that is periodically called
  //  after the IdleStart has been called from some other location in your app.


  imap.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.