List of important port numbers

15 - Netstat
21 - FTP
23 - Telnet
25 - SMTP
42 - WINS
53 - DNS
67 - Bootp
68 - DHCP
80 - HTTP
88 - Kerberos
101 - HOSTNAME
110 - POP3
119 - NNTP
123 - NTP (Network time protocol)
139 - NetBIOS
161 - SNMP
180 - RIS
389 - LDAP (Lightweight Directory Access Protocol)
443 - HTTPS (HTTP over SSL/TLS)
520 - RIP
79 - FINGER
37 - Time
3389 - Terminal services
443 - SSL (https) (http protocol over TLS/SSL)
220 - IMAP3
3268 - AD Global Catalog
3269 - AD Global Catalog over SSL
500 - Internet Key Exchange, IKE (IPSec) (UDP 500)