Sometimes, nothing is more convenient than to do a port scan on a machine to find out what services it offers. The nmap command is very useful to do this:
nmap -sS 192.168.1.1
Starting Nmap 4.53 ( http://insecure.org ) at 2009-06-12 10:11 MDT
Interesting ports on 192.168.1.1 (192.168.1.1):
Not shown: 1683 closed ports
PORT STATE SERVICE
1/tcp filtered tcpmux
4/tcp filtered unknown
7/tcp filtered echo
8/tcp filtered unknown
10/tcp filtered unknown
13/tcp filtered daytime
14/tcp filtered unknown
18/tcp filtered msp
19/tcp filtered chargen
21/tcp open ftp
22/tcp open ssh
23/tcp filtered telnet
25/tcp filtered smtp
53/tcp filtered domain
80/tcp open http
110/tcp open pop3
137/tcp filtered netbios-ns
194/tcp filtered irc
445/tcp filtered microsoft-ds
529/tcp filtered irc
873/tcp open rsync
994/tcp filtered ircs
1026/tcp filtered LSA-or-nterm
1434/tcp filtered ms-sql-m
4000/tcp open remoteanything
6000/tcp filtered X11
6662/tcp filtered radmind
6667/tcp filtered irc
6669/tcp filtered irc
7000/tcp filtered afs3-fileserver
32773/tcp filtered sometimes-rpc9
Nmap done: 1 IP address (1 host up) scanned in 4.500 seconds