public String setPort(String port) {
		if (port.length() == 0 || port.equals(Integer.toString(getPort())))
			return null;
		for (Character c : port.toCharArray())
			if (!Character.isDigit(c)) {
				return "Invalid port: " + port;
			}
		this.port = Integer.parseInt(port);
		return "Changed port to: " + port;
	}