code: @Override
      public void exceptionCaught(IoSession session, Throwable cause) throws Exception {
          ExceptionHandler<Throwable> handler = findExceptionHandler(cause.getClass());
          if (handler != null) {
              handler.exceptionCaught(session, cause);
          } else {
              throw new UnknownMessageTypeException(
                      "No handler found for exception type: " +
                      cause.getClass().getSimpleName());
          }
      }
docs: Invoked when any exception is thrown by user IoHandler implementation
  or by MINA. If cause is an instance of IOException, MINA will close the
  connection automatically.
  
  <b>Warning !</b> If you are to overload this method, be aware that you
  _must_ call the messageHandler in your own method, otherwise it won't
  be called.