Usually using Services and Port Numbers

Port	TCP	UDP	Description
20	x		FTP-data
21	x		FTP (login access)
22	x	x	SSH
23	x		Telnet
25	x		SMTP (Mail, MTA)
53	x	x	DNS
80	x	x	HTTP (Web)
110	x	x	POP3(email); generally uses TCP
119	x		NNTP (Usenet news)
139	x	x	NetBIOS (Microsoft)
143	x	x	IMAP (email)
161	x	x	SMTP (Network Monitor)
443	x	x	HTTPS
465	x		SMTPS (Secure mail over SSL)
993	x	x	IMAPS (Secure IMAP over SSL)
995	x	x	POP3S (Secure POP3 over SSL)