ident

Ident is an Internet protocol that helps identify the user of a particular TCP connection.

$ ident-user-enum 10.10.10.10 113 8080 10000 22   <-- Enum the ports
ident-user-enum v1.0 ( http://pentestmonkey.net/tools/ident-user-enum )

10.10.10.10:113	    nobody
10.10.10.10:8080	  some_username
10.10.10.10:10000	  some_other_username
10.10.10.10:22	    root