The TCP/IP Guide - Common TCP/IP Applications and Assigned Well-Known and Registered Port Numbers

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Table 145 lists the well-known port numbers for the most common TCP/IP application protocols.

**Table 145: Common TCP/IP Well-Known Port Numbers and Applications**
Port #	TCP / UDP	Keyword	Protocol Abbreviation	Application or Protocol Name / Comments
7	TCP + UDP	echo	—	Echo Protocol
9	TCP + UDP	discard	—	Discard Protocol
11	TCP + UDP	systat	—	Active Users Protocol
13	TCP + UDP	daytime	—	Daytime Protocol
17	TCP + UDP	qotd	QOTD	Quote Of The Day Protocol
19	TCP + UDP	chargen	—	Character Generator Protocol
20	TCP	ftp-data	FTP (data)	File Transfer Protocol (default data port)
21	TCP	ftp	FTP (control)	File Transfer Protocol (control / commands)
23	TCP	telnet	—	Telnet Protocol
25	TCP	smtp	SMTP	Simple Mail Transfer Protocol
37	TCP + UDP	time	—	Time Protocol
43	TCP	nicname	—	Whois Protocol (also called “Nicname”)
53	TCP + UDP	domain	DNS	Domain Name Server (Domain Name System)
67	UDP	bootps	BOOTP / DHCP	Bootstrap Protocol / Dynamic Host Configuration Protocol (Server)
68	UDP	bootpc	BOOTP / DHCP	Bootstrap Protocol / Dynamic Host Configuration Protocol (Client)
69	UDP	tftp	TFTP	Trivial File Transfer Protocol
70	TCP	gopher	—	Gopher Protocol
79	TCP	finger	—	Finger User Information Protocol
80	TCP	http	HTTP	Hypertext Transfer Protocol (World Wide Web)
110	TCP	pop3	POP	Post Office Protocol (version 3)
119	TCP	nntp	NNTP	Network News Transfer Protocol
123	UDP	ntp	NTP	Network Time Protocol
137	TCP + UDP	netbios-ns	—	NetBIOS (Name Service)
138	UDP	netbios-dgm	—	NetBIOS (Datagram Service)
139	TCP	netbios-ssn	—	NetBIOS (Session Service)
143	TCP	imap	IMAP	Internet Message Access Protocol
161	UDP	snmp	SNMP	Simple Network Management Protocol
162	UDP	snmptrap	SNMP	Simple Network Management Protocol (Trap)
179	TCP	bgp	BGP	Border Gateway Protocol
194	TCP	irc	IRC	Internet Relay Chat
443	TCP	https	HTTP over SSL	Hypertext Transfer Protocol over Secure Sockets Layer
500	UDP	isakmp	IKE	IPSec Internet Key Exchange
520	UDP	router	RIP	Routing Information Protocol (RIP-1 and RIP-2)
521	UDP	ripng	RIPng	Routing Information Protocol - “Next Generation”

The registered port numbers are by definition for protocols that are not standardized using the RFC process, so they are mostly esoteric applications that I don’t feel there is much point in listing at length. Table 146 shows a few that I feel are of particular interest:

Table 146: Common TCP/IP Registered Port Numbers and Applications

Port #

TCP / UDP

Keyword

Protocol Abbreviation

Application or Protocol Name / Comments

1512

TCP + UDP

wins

WINS

Microsoft Windows Internet Naming Service

1701

UDP

l2tp

L2TP

Layer Two Tunneling Protocol

1723

TCP

pptp

PPTP

Point-To-Point Tunneling Protocol

2049

TCP + UDP

nfs

NFS

Network File System

6000 - 6063

TCP

x11

X11

X Window System