So I'm trying to learn some pen tester techniques because I think its a great field to get into with a great future. In my research i came across the linux tool netcat, i read what it does and got it working by connecting to FTP servers, telnet, and SSH servers, (all my own in VM's) and was able to get the banners from the services i connect to. My question is after connecting how do i interact with the protocol in use? (e.g. after connecting to a telnet or SSH server how do i get it to prompt me for user names and password (if used) ) common sense tells me that since netcat works at a very "raw" level i figure i must give it the command that are usually sent in protocol payloads, question is where do i find a reference for those commands? the only thing i can think of is RFC's but those are so painful to read. can anyone point me in the right direction or is it just a growing pain of becoming a pen tester? Thanks in advance to all who reply.