If host is vulnerable every time when we call send_pkt function we send data that forces client samba process (seems like samba creates new process for every new client) to fall into infinite loop where he allocates memory for adding new list elements, and that copy doesn't response any more. Therefore we need to login and create new session every time.
If we want to speed up the process of memory consumption we need to enlarge item size (MsgLen option) and create multiple client processes.