20/21FTP — file transfer
22SSH — secure shell
23Telnet — remote login, insecure
25SMTP — email sending
53DNS — domain name resolution
67/68DHCP — auto IP assignment
80HTTP — web traffic
110POP3 — email retrieval
143IMAP — email access
443HTTPS — secure web traffic
445SMB — file sharing
993IMAPS — secure email access
995POP3S — secure email retrieval
3306MySQL — database
3389RDP — remote desktop
5432PostgreSQL — database
8080HTTP Alt — web proxy/dev