long getLastActive() {
        return reader.getLastActive();
    }
Returns the last time a full Document was read or a heartbeat was received. Hearbeats
are represented as whitespaces 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/jivesoftware/openfire/net/SocketReader.java