I am using metasploitable to learn pen testing but I ran into a problem that is most likely very simple but I don't yet understand this. I used the vsfpd backdoor exploit to connect to metasploitable. Then I disconnect. When I try to reconnect using the same exploit I get the message that the exploit ran successfully, however no shell was created. How do I reconnect to metasploitable after using an exploit on it and disconnecting?