@Override
 public void sessionDestroyed(HttpSessionEvent _se) {
   try {
     HttpSession tempSession = sessions.remove(_se.getSession().getId());
   } catch (NullPointerException | UnsupportedOperationException | ClassCastException e) {
   }
   setUsersOnline(getUsersOnline() - 1);
 }
  /**
   * removes this connection from the connections map the datagram channel still sticks around in
   * case it needs to be reused
   */
  static void removeConnection(RDPConnection con) {
    lock.lock();
    try {
      if (Log.loggingNet) Log.net("RDPServer.removeConnection: removing con " + con);
      con.setState(RDPConnection.CLOSED);

      DatagramChannel dc = con.getDatagramChannel();

      // first we get the set of connections attached to the given dc
      Map<ConnectionInfo, RDPConnection> dcConMap = allConMap.get(dc);
      if (dcConMap == null) {
        throw new MVRuntimeException("RDPServer.removeConnection: cannot find dc");
      }

      int localPort = con.getLocalPort();
      int remotePort = con.getRemotePort();
      InetAddress remoteAddr = con.getRemoteAddr();
      ConnectionInfo conInfo = new ConnectionInfo(remoteAddr, remotePort, localPort);
      Object rv = dcConMap.remove(conInfo);
      if (rv == null) {
        throw new MVRuntimeException("RDPServer.removeConnection: could not find the connection");
      }

      // close the datagramchannel if needed
      // conditions: no other connections on this datagramchannel
      // no socket listening on this datagramchannel
      if (dcConMap.isEmpty()) {
        Log.net("RDPServer.removeConnection: no other connections for this datagramchannel (port)");
        // there are no more connections on this datagram channel
        // check if there is a serversocket listening
        if (getRDPSocket(dc) == null) {
          Log.net("RDPServer.removeConnection: no socket listening on this port - closing");
          // no socket either, close the datagramchannel
          dc.socket().close();
          channelMap.remove(localPort);
          Log.net("RDPServer.removeConnection: closed and removed datagramchannel/socket");
        } else {
          Log.net("RDPServer.removeConnection: there is a socket listening on this port");
        }
      } else {
        Log.net("RDPServer.removeConnection: there are other connections on this port");
      }
    } finally {
      lock.unlock();
    }
  }
 /**
  * Sets the value of a specific piece of statistics. The method assumes that the caller has
  * acquired the write lock of {@link #lock} and, thus, allows the optimization of batch updates to
  * multiple pieces of statistics.
  *
  * @param stat the piece of statistics to set
  * @param value the value of the piece of statistics to set
  */
 protected void unlockedSetStat(String stat, Object value) {
   if (value == null) stats.remove(stat);
   else stats.put(stat, value);
 }