Dart

Using IMAP IDLE to Wait for Updates

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

import 'package:chilkat/chilkat.dart';

void main() {
  final imap = CkImap();

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

  // Select an IMAP mailbox
  try {
    imap.selectMailbox('INBOX');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // 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).
  try {
    imap.idleStart();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // 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:
  var idleResultXml = '';
  try {
    idleResultXml = imap.idleCheck(1);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // 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:
  try {
    imap.idleDone();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // 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.
}