Identifing network daemons

Say you've port scanned yourself

$ nmap localhost
Starting nmap 3.27 http://www.insecure.org/nmap/
Interesting ports on localhost (127.0.0.1):
(The 1544 ports scanned but not shown below are in state: closed)
Port       State       Service
21/tcp     open        ftp                     
22/tcp     open        ssh                     
25/tcp     open        smtp                    
53/tcp     open        domain                  
143/tcp    open        imap2                   
465/tcp    open        smtps                   
783/tcp    open        hp-alarm-mgr            
993/tcp    open        imaps                   
995/tcp    open        pop3s