private void tryFinal() {
    assert (_actives == 0);

    if (LOG.isDebugEnabled()) LOG.debug("tryFinal, branches: {}, untried: {}", _branches, _targets);

    if (_best == null) {
      _best =
          (SipResponse) getOriginalRequest().createResponse(SipServletResponse.SC_REQUEST_TIMEOUT);
      _best.setToTag(ID.newTag());
    }

    if (LOG.isDebugEnabled()) LOG.debug("final response is {}", _best, null);

    _best.setBranchResponse(false);
    invokeServlet(_best);

    if (_actives > 0) {
      if (LOG.isDebugEnabled()) LOG.debug("new branch(es) created in callback {}", _branches, null);
      return;
    }
    forward(_best);
  }
    public void handleResponse(SipResponse response) {
      _response = response;

      int status = response.getStatus();

      if (status == 100) return;

      if (_tx.isCompleted() && !response.is2xx()) {
        if (LOG.isDebugEnabled())
          LOG.debug("Dropping response " + response.getStatus() + " since proxy is completed");
        return;
      }

      if (LOG.isDebugEnabled()) LOG.debug("Got response {}", response, null);

      SipRequest request = _tx.getRequest();

      Session session = request.session();

      if (request.isInitial() && status < 300) {
        if (!session.isSameDialog(response)) {
          AppSession appSession = session.appSession();
          Session derived = appSession.getSession(response);
          if (derived == null) derived = appSession.createDerivedSession(session);
          session = derived;
        }
      }

      response.setSession(session);
      if (status < 300) session.updateState(response, false);

      response.removeTopVia();
      response.setProxyBranch(this);

      if (status < 200) {
        if (response.isInvite()) updateTimerC();

        invokeServlet(response);
        forward(response);
      } else {
        _actives--;

        stopTimerC();

        if ((300 <= status && status < 400) && _branchRecurse) {
          try {
            Iterator<Address> it = response.getAddressHeaders(SipHeaders.CONTACT);
            while (it.hasNext()) {
              Address contact = (Address) it.next();
              if (contact.getURI().isSipURI()) {
                Branch branch = addTarget(contact.getURI());
                if (branch != null) {
                  _recursedBranches = LazyList.add(_recursedBranches, branch);
                  branch.setRecurse(_branchRecurse);
                }
              }
            }
          } catch (ServletParseException e) {
            LOG.ignore(e);
          }
        }

        if (_best == null
            || (_best.getStatus() < 600 && (status < _best.getStatus() || status >= 600))) {
          _best = response;
        }

        if (status >= 600) {
          SipProxy.this.doCancel(null, null, null);
        }

        if (status < 300) {
          invokeServlet(response);
          forward(response);

          SipProxy.this.doCancel(null, null, null);
        } else {
          if (LazyList.size(_targets) > 0) startProxy();

          if (_actives > 0) {
            response.setBranchResponse(true);
            invokeServlet(response);
          } else {
            tryFinal();
          }
        }
      }
    }