WELL KNOWN PORTS
20 – FTP Data (For transferring FTP data)
21 – FTP Control (For starting FTP connection)
22 – SSH (For secure remote administration which uses SSL to encrypt the transmission)
23 – Telnet (For insecure remote administration)
25 – SMTP (Mail Transfer Agent for e-mail server such as SEND mail)
53 – DNS (Special service which uses both TCP and UDP)
67 – Bootp
68 – DHCP
69 – TFTP (Trivial file transfer protocol uses udp protocol for connection less transmission of data)
80 – HTTP/WWW(Apache)
88 – Kerberos
110 – POP3 (Mail delivery Agent)
123 – NTP (Network time protocol used for time syncing uses UDP protocol)
137 – NetBIOS (nmbd)
139 – SMB-Samba (smbd)
143 – IMAP
161 – SNMP (For network monitoring)
389 – LDAP (For centralized administration)
443 – HTTPS (HTTP+SSL for secure web access)
514 – Syslogd (udp port)
636 – ldaps (both ctp and udp)
873 – rsync
989 – FTPS-data
990 – FTPS
993 – IMAPS
1194 – openVPN
1812 – RADIUS
995 – POP3s
2049 – NFS (nfsd, rpc.nfsd, rpc, portmap)
2401 – CVS server
3306 – MySql
3690 – SVN