Use callback to monitor for new mail

Here is an example how to use callbacks. When you subscribe for an event than you can specify callback address and listen on that address in order to be notified when an event occurs. Callback uses UDP protocol and you will be notified immediately after event occurs. In the example below we first subscribe to monitor Inbox folder for incoming messages. Method Listen represents a little UDP server and here we listen for Exchange server response. When new mail arrives then Exchange server will notify you immediately.

C# example

using System;
using System.Net;
using System.Net.Sockets;
using Independentsoft.Webdav.Exchange;

namespace Sample
{
    class Program
    {
        private static string clientName = "192.168.2.100";
        private static string serverName = "192.168.2.2";
        private static int port = 4568;

        private static Resource resource;
        private static Subscription subscription;
        private static Mailbox myMailbox;

        static void Main(string[] args)
        {
            NetworkCredential credential = new NetworkCredential("username", "password");
            WebdavSession session = new WebdavSession(credential);
            session.UserMailbox = "https://192.168.2.2/exchange/emailaddress/";

            resource = new Resource(session);

            //User's mailbox
            myMailbox = resource.Mailbox;

            //set subscription
            string callBack = "httpu://" + clientName + ":" + port + "/";
            subscription = resource.Subscribe(myMailbox.Inbox, NotificationType.NewMail, 3600, Depth.One, 0, callBack);

            Console.WriteLine("Listen...");
            Listen();
        }

        public static void Listen()
        {
            IPHostEntry clientHostEntry = null;
            IPHostEntry serverHostEntry = null;

            try
            {
                Socket udpSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

                try
                {
                    clientHostEntry = Dns.GetHostByName(clientName);
                    serverHostEntry = Dns.GetHostByName(serverName);
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.StackTrace);
                }

                IPEndPoint clientIpEndPoint = new IPEndPoint(clientHostEntry.AddressList[0], port);
                udpSocket.Bind(clientIpEndPoint);

                while (true)
                {
                    Byte[] received = new Byte[512];
                    IPEndPoint serverIpEndPoint = new IPEndPoint(serverHostEntry.AddressList[0], port);
                    EndPoint serverEP = (serverIpEndPoint);

                    int bytesReceived = udpSocket.ReceiveFrom(received, ref serverEP);
                    String dataReceived = System.Text.Encoding.ASCII.GetString(received);
                    Console.WriteLine(dataReceived);

                    //Acknowledge each event signal with POLL
                    resource.Poll(myMailbox.Inbox, subscription.ID);
                }
            }
            catch (SocketException se)
            {
                Console.WriteLine(se.StackTrace);
            }
        }
    }
}

VB example

Imports System
Imports System.Net
Imports System.Net.Sockets
Imports Independentsoft.Webdav.Exchange

Module Module1

    Private clientName As String = "192.168.2.100"
    Private serverName As String = "192.168.2.2"
    Private port As Integer = 4568
    Private resource As Resource
    Private subscription As Subscription
    Private myMailbox As Mailbox

    Sub Main(ByVal args As String())

        Dim credential As NetworkCredential = New NetworkCredential("username", "password")
        Dim session As WebdavSession = New WebdavSession(credential)
        session.UserMailbox = "https://192.168.2.2/exchange/emailaddress/"

        resource = New Resource(session)
        myMailbox = resource.Mailbox

        Dim callBack As String = "httpu://" & clientName & ":" & port & "/"
        subscription = resource.Subscribe(myMailbox.Inbox, NotificationType.NewMail, 3600, Depth.One, 0, callBack)

        Console.WriteLine("Listen...")
        Listen()
    End Sub

    Public Sub Listen()
        Dim clientHostEntry As IPHostEntry = Nothing
        Dim serverHostEntry As IPHostEntry = Nothing

        Try
            Dim udpSocket As Socket = New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)

            Try
                clientHostEntry = Dns.GetHostByName(clientName)
                serverHostEntry = Dns.GetHostByName(serverName)
            Catch ex As Exception
                Console.WriteLine(ex.StackTrace)
            End Try

            Dim clientIpEndPoint As IPEndPoint = New IPEndPoint(clientHostEntry.AddressList(0), port)
            udpSocket.Bind(clientIpEndPoint)

            While True

                Dim received(512) As Byte
                Dim serverIpEndPoint As IPEndPoint = New IPEndPoint(serverHostEntry.AddressList(0), port)
                Dim serverEP As EndPoint = (serverIpEndPoint)

                Dim bytesReceived As Integer = udpSocket.ReceiveFrom(received, serverEP)
                Dim dataReceived As String = System.Text.Encoding.ASCII.GetString(received)

                Console.WriteLine(dataReceived)
                resource.Poll(myMailbox.Inbox, subscription.ID)
            End While

        Catch se As SocketException
            Console.WriteLine(se.StackTrace)
        End Try
    End Sub

End Module

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