protected HashMap response_map = new HashMap( 4 );

    protected abstract void makeKey( Request request ) throws IOException;
    protected abstract Request peekKey() throws IOException;
    protected abstract void doSend( Request request ) throws IOException;
    protected abstract void doRecv( Response response ) throws IOException;
    protected abstract void doSkip() throws IOException;

    public synchronized void sendrecv( Request request,

     * @param timeout
     * @return
     * @throws IOException
     */
    protected <T extends Response> long doSend ( Request request, T response, Set<RequestParam> params, long timeout ) throws IOException {
        long firstKey = prepareRequests(request, response, params, timeout);
        doSend(request);
        return firstKey;
    }


    /**
     * @param request
     * @param response