public long getLastActive() {
        long lastHeartbeat = 0;
        try {
            lastHeartbeat = getXPPParser().getLastHeartbeat();
        }
        catch (XmlPullParserException e) {
            Log.trace("An exception occurred while trying to get the last hartbeat.", e);
        }
        return Math.max(lastActive, lastHeartbeat);
    }
Returns the last time a full Document was read or a heartbeat was received. Hearbeats
are represented as whitespaces or \n received while a Document is not being parsed.

@return the time in milliseconds when the last document or heartbeat was received.
xmppserver/src/main/java/org/dom4j/io/XMPPPacketReader.java