internal extern static int PeerCollabSetPresenceInfo(ref PEER_PRESENCE_INFO ppi);
 internal extern static int PeerCollabSetPresenceInfo(ref PEER_PRESENCE_INFO ppi);
        internal override void PresenceChangedCallback(object state, bool timedOut)
        {
            SafeCollabData eventData = null;
            int            errorCode = 0;

            Logging.P2PTraceSource.TraceEvent(TraceEventType.Information, 0, "PresenceChangedCallback() called.");

            if (m_Disposed)
            {
                return;
            }

            while (true)
            {
                PresenceChangedEventArgs presenceChangedArgs = null;

                //
                // Get the event data for the fired event
                //
                try{
                    lock (LockPresenceChangedEvent){
                        if (m_safePresenceChangedEvent.IsInvalid)
                        {
                            return;
                        }
                        errorCode = UnsafeCollabNativeMethods.PeerCollabGetEventData(m_safePresenceChangedEvent,
                                                                                     out eventData);
                    }

                    if (errorCode == UnsafeCollabReturnCodes.PEER_S_NO_EVENT_DATA)
                    {
                        break;
                    }
                    else if (errorCode != 0)
                    {
                        Logging.P2PTraceSource.TraceEvent(TraceEventType.Error, 0, "PeerCollabGetEventData returned with errorcode {0}", errorCode);
                        throw PeerToPeerException.CreateFromHr(SR.GetString(SR.Collab_GetPresenceChangedDataFailed), errorCode);
                    }

                    PEER_COLLAB_EVENT_DATA ped = (PEER_COLLAB_EVENT_DATA)Marshal.PtrToStructure(eventData.DangerousGetHandle(),
                                                                                                typeof(PEER_COLLAB_EVENT_DATA));
                    if (ped.eventType == PeerCollabEventType.MyPresenceChanged)
                    {
                        PEER_EVENT_PRESENCE_CHANGED_DATA presenceData = ped.presenceChangedData;

                        PeerPresenceInfo peerPresenceInfo = null;
                        if (presenceData.pPresenceInfo != IntPtr.Zero)
                        {
                            PEER_PRESENCE_INFO ppi = (PEER_PRESENCE_INFO)Marshal.PtrToStructure(presenceData.pPresenceInfo, typeof(PEER_PRESENCE_INFO));
                            peerPresenceInfo = new PeerPresenceInfo();
                            peerPresenceInfo.PresenceStatus  = ppi.status;
                            peerPresenceInfo.DescriptiveText = ppi.descText;
                        }

                        PeerEndPoint peerEndPoint = null;
                        if (presenceData.pEndPoint != IntPtr.Zero)
                        {
                            PEER_ENDPOINT pe = (PEER_ENDPOINT)Marshal.PtrToStructure(presenceData.pEndPoint, typeof(PEER_ENDPOINT));
                            peerEndPoint = CollaborationHelperFunctions.ConvertPEER_ENDPOINTToPeerEndPoint(pe);
                        }

                        presenceChangedArgs = new PresenceChangedEventArgs(peerEndPoint,
                                                                           null,
                                                                           presenceData.changeType,
                                                                           peerPresenceInfo);
                    }
                }
                finally{
                    if (eventData != null)
                    {
                        eventData.Dispose();
                    }
                }

                //
                // Fire the callback with the marshalled event args data
                //
                if (presenceChangedArgs != null)
                {
                    OnPresenceChanged(presenceChangedArgs);
                }
            }
            Logging.P2PTraceSource.TraceEvent(TraceEventType.Information, 0, "Leaving PresenceChangedCallback().");
        }