how to automatically data-change between the nodes on Z-stack mesh?

Thank you Yikai Chen.

My purpose is to send/receive some application specific data via unicast and broadcast.

For example if a motion sensor detects a motion, then it should broadcast this information to the other nodes,  or when a node measures , say, temperature and desalinate to coordinator.

I have user specific library to handle files, what I did is to add an extra function to receive the incoming data and defined a clusterID for my own application (I am not sure if this is the correct way to do it, or should I have done differently):

static void GenericApp_MessageMSGCB( afIncomingMSGPacket_t *pkt )
{
  switch ( pkt->clusterId )
  {
    case GENERICAPP_CLUSTERID:
      rxMsgCount += 1;  // Count this message
      HalLedSet ( HAL_LED_4, HAL_LED_MODE_BLINK );  // Blink an LED
#if defined( LCD_SUPPORTED )
      HalLcdWriteString( (char*)pkt->cmd.Data, HAL_LCD_LINE_1 );
      HalLcdWriteStringValue( "Rcvd:", rxMsgCount, 10, HAL_LCD_LINE_2 );
#elif defined( WIN32 )
      WPRINTSTR( pkt->cmd.Data );
#endif
      break;
  case MY_APP_SYSTEM_MSG : //Cluster ID:3
      handleSysMsg(pkt);
#if defined( LCD_SUPPORTED )
      HalLcdWriteString( (char*)pkt->cmd.Data, HAL_LCD_LINE_1 );
      HalLcdWriteStringValue( "Rcvd:", rxMsgCount, 10, HAL_LCD_LINE_2 );
#elif defined( WIN32 )
      WPRINTSTR( pkt->cmd.Data );
#endif
      break;
  case MY_EXTERNAL_MSG: // Cluster ID: 4
    handleExternalMsg(pkt);
    break;
    
  case MY_APP_QUERY_MSG: //Cluster ID: 5
    handleQueryMsg(pkt);
    break;
    
    
 // default:
  }
}

I send them via 

void GenericApp_SendMessage( char *msg )
{
  
  char *theMessageData = malloc( strlen(msg) + 1 );
  strncpy(theMessageData, msg, strlen(msg) + 1);
   

    
  if ( AF_DataRequest( &GenericApp_DstAddr, &GenericApp_epDesc,
                       My_APP_SYSTEM_MSG,
                       (byte)osal_strlen( theMessageData ) + 1,
                       (byte *)theMessageData,
                       &GenericApp_TransID,
                       AF_DISCV_ROUTE, AF_DEFAULT_RADIUS ) == afStatus_SUCCESS )
  {
    // Successfully requested to be sent.
  }
  else
  {
    // Error occurred in request to send.
  }
  free(theMessageData);

}

As an example, I want them to broadcast

GenericApp_SendMessage("hello world 2"); by default when they are powered and join/form the network