public void updateUserMap()
	{
		ArrayList<Integer> offlineList = new ArrayList<>();
		for (Integer port : userMap.keySet())
			// 'If user is not online'
			if (!userMap.get(port).isOnline())
				// Add user to offline list
				offlineList.add(port);
		for (Integer userPort : offlineList)
			removeUser(userPort);
	}