public boolean isExistingSession() {
        return existingSession;
    }
Returns whether the successful authentication attempt represented by
this event is related to an established Guacamole session. During normal
operation, the Guacamole web application will periodically
re-authenticate with the server to verify its authentication token and
update the session state, in which case the value returned by this
function will be true. If the user was not already authenticated and has
just initially logged in, false is returned.

@return
    true if this AuthenticationSuccessEvent is related to a Guacamole
    session that was already established, false otherwise.
guacamole-ext/src/main/java/org/apache/guacamole/net/event/AuthenticationSuccessEvent.java