code: public boolean refreshBuddy(String eventId, long timeout) {
      if (parent.getBuddyList().get(targetUri) == null) {
        setReturnCode(SipSession.INVALID_ARGUMENT);
        setErrorMessage("Buddy refresh for URI " + targetUri + " failed, not found in buddy list.");
        return false;
      }
  
      return refreshBuddy(getTimeLeft(), eventId, timeout);
    }
docs: This method is the same as refreshBuddy(duration, eventId, timeout) except that the SUBSCRIBE
  duration sent will be however much time is left on the current subscription. If time left on
  the subscription &lt;= 0, unsubscribe occurs (note, the buddy stays in the list).