Well known services are defined by RFC 1060. The relationship between the well known services and the well known ports is described in this excerpt from RFC 1340 (J. Reynolds and J. Postal, July 1992):
The well known ports are controlled and assigned by the Internet Assigned Numbers Authority (IANA), and on most systems can only be used by system (or root) processes or by programs executed by privileged users.
Ports are used in TCP to name the ends of logical connections that carry long term conversations. For the purpose of providing services to unknown callers, a service contact port is defined. This list specifies the port used by the server process as its contact port. The contact port is sometimes called the "well known port."
UDP ports are not the same as TCP ports, though to the extent possible, TCP and UDP may use the same port assignments. The UDP specification is defined in RFC 768.
The assigned ports use a small portion of the possible port numbers. For many years, the assigned ports were in the range 0 – 255. Recently, the range for assigned ports managed by the IANA has been expanded to the range 0 – 1023.
The following table describes both TCP and UDP port assignments for well known ports.
Table C.1 Port Assignments for Well Known Ports
Decimal | Keyword | Description |
0/tcp, udp | Reserved | |
1/tcp, udp | tcpmux | TCP Port Service Multiplexer |
2/tcp, udp | compressnet | Management Utility |
3/tcp, udp | compressnet | Compression Process |
4/tcp, udp | Unassigned | |
5/tcp, udp | rje | Remote Job Entry |
6/tcp, udp | Unassigned | |
7/tcp, udp | echo | Echo |
8/tcp, udp | Unassigned | |
9/tcp, udp | discard | Discard; alias=sink null |
10/tcp, udp | Unassigned | |
11/udp | systat | Active Users; alias=users |
12/tcp, udp | Unassigned | |
13/tcp, udp | daytime | Daytime |
14/tcp, udp | Unassigned | |
15/tcp, udp | Unassigned [was netstat] | |
16/tcp, udp | Unassigned | |
17/tcp, udp | qotd | Quote of the Day; alias=quote |
18/tcp, udp | msp | Message Send Protocol |
19/tcp, udp | chargen | Character Generator; alias=ttytst source |
20/tcp, udp | ftp-data | File Transfer [Default Data] |
21/tcp, udp | ftp | File Transfer [Control], connection dialog |
22/tcp, udp | Unassigned | |
23/tcp, udp | telnet | Telnet |
24/tcp, udp | Any private mail system | |
25/tcp, udp | smtp | Simple Mail Transfer; alias=mail |
26/tcp, udp | Unassigned | |
27/tcp, udp | nsw-fe | NSW User System FE |
28/tcp, udp | Unassigned | |
29/tcp, udp | msg-icp | MSG ICP |
30/tcp, udp | Unassigned | |
31/tcp, udp | msg-auth | MSG Authentication |
32/tcp, udp | Unassigned | |
33/tcp, udp | dsp | Display Support Protocol |
34/tcp, udp | Unassigned | |
35/tcp, udp | Any private printer server | |
36/tcp, udp | Unassigned | |
37/tcp, udp | time | Time; alias=timeserver |
38/tcp, udp | Unassigned | |
39/tcp, udp | rlp | Resource Location Protocol; alias=resource |
40/tcp, udp | Unassigned | |
41/tcp, udp | graphics | Graphics |
42/tcp, udp | nameserver | Host Name Server; alias=nameserver |
43/tcp, udp | nicname | Who Is; alias=nicname |
44/tcp, udp | mpm-flags | MPM FLAGS Protocol |
45/tcp, udp | mpm | Message Processing Module |
46/tcp, udp | mpm-snd | MPM [default send] |
47/tcp, udp | ni-ftp | NI FTP |
48/tcp, udp | Unassigned | |
49/tcp, udp | login | Login Host Protocol |
50/tcp, udp | re-mail-ck | Remote Mail Checking Protocol |
51/tcp, udp | la-maint | IMP Logical Address Maintenance |
52/tcp, udp | xns-time | XNS Time Protocol |
53/tcp, udp | domain | Domain Name Server |
54/tcp, udp | xns-ch | XNS Clearinghouse |
55/tcp, udp | isi-gl | ISI Graphics Language |
56/tcp, udp | xns-auth | XNS Authentication |
57/tcp, udp | Any private terminal access | |
58/tcp, udp | xns-mail | XNS Mail |
59/tcp, udp | Any private file service | |
60/tcp, udp | Unassigned | |
61/tcp, udp | ni-mail | NI MAIL |
62/tcp, udp | acas | ACA Services |
63/tcp, udp | via-ftp | VIA Systems - FTP |
64/tcp, udp | covia | Communications Integrator (CI) |
65/tcp, udp | tacacs-ds | TACACS-Database Service |
66/tcp, udp | sql*net | Oracle SQL*NET |
67/tcp, udp | bootpc | DHCP/BOOTP Protocol Server |
68/tcp, udp | bootpc | DHCP/BOOTP Protocol Server |
69/ udp | tftp | Trivial File Transfer |
70/tcp, udp | gopher | Gopher |
71/tcp, udp | netrjs-1 | Remote Job Service |
72/tcp, udp | netrjs-2 | Remote Job Service |
73/tcp, udp | netrjs-3 | Remote Job Service |
74/tcp, udp | netrjs-4 | Remote Job Service |
75/udp | Any private dial out service | |
76/tcp, udp | Unassigned | |
77/tcp, udp | Any private RJE service | |
78/tcp, udp | vettcp | Vettcp |
79/tcp, udp | finger | Finger |
80/tcp, udp | www | World Wide Web HTTP |
81/tcp, udp | hosts2-ns | HOSTS2 Name Server |
82/tcp, udp | xfer | XFER Utility |
83/tcp, udp | mit-ml-dev | MIT ML Device |
84/tcp, udp | ctf | Common Trace Facility |
85/tcp, udp | mit-ml-dev | MIT ML Device |
86/tcp, udp | mfcobol | Micro Focus Cobol |
87/tcp, udp | Any private terminal link; alias=ttylink | |
88/tcp, udp | kerberos | Kerberos |
89/tcp | su-mit-tg | SU/MIT Telnet Gateway |
89/udp | su-mit-tg | SU/MIT Telnet Gateway |
90/tcp, udp | DNSIX Security Attribute Token Map | |
91/tcp, udp | mit-dov | MIT Dover Spooler |
92/tcp, udp | npp | Network Printing Protocol |
93/tcp, udp | dcp | Device Control Protocol |
94/tcp, udp | objcall | Tivoli Object Dispatcher |
95/tcp, udp | supdup | SUPDUP |
96/tcp, udp | dixie | DIXIE Protocol Specification |
97/tcp, udp | swift-rvf | Swift Remote Virtual File Protocol |
98/tcp, udp | tacnews | TAC News |
99/tcp, udp | metagram | Metagram Relay |
100/tcp | newacct | [unauthorized use] |
101/tcp, udp | hostname | NIC Host Name Server; alias=hostname |
102/tcp, udp | iso-tsap | ISO-TSAP |
103/tcp, udp | gppitnp | Genesis Point-to-Point Trans Net; alias=webster |
104/tcp, udp | acr-nema | ACR-NEMA Digital Imag. & Comm. 300 |
105/tcp, udp | csnet-ns | Mailbox Name Nameserver |
106/tcp, udp | 3com-tsmux | 3COM-TSMUX |
107/tcp, udp | rtelnet | Remote Telnet Service |
108/tcp, udp | snagas | SNA Gateway Access Server |
109/tcp, udp | pop2 | Post Office Protocol - Version 2; alias=postoffice |
110/tcp, udp | pop3 | Post Office Protocol - Version 3; alias=postoffice |
111/tcp, udp | sunrpc | SUN Remote Procedure Call |
112/tcp, udp | mcidas | McIDAS Data Transmission Protocol |
113/tcp, udp | auth | Authentication Service; alias=authentication |
114/tcp, udp | audionews | Audio News Multicast |
115/tcp, udp | sftp | Simple File Transfer Protocol |
116/tcp, udp | ansanotify | ANSA REX Notify |
117/tcp, udp | uucp-path | UUCP Path Service |
118/tcp, udp | sqlserv | SQL Services |
119/tcp, udp | nntp | Network News Transfer Protocol; alias=usenet |
120/tcp, udp | cfdptkt | CFDPTKT |
121/tcp, udp | erpc | Encore Expedited Remote Pro.Call |
122/tcp, udp | smakynet | SMAKYNET |
123/tcp, udp | ntp | Network Time Protocol; alias=ntpd ntp |
124/tcp, udp | ansatrader | ANSA REX Trader |
125/tcp, udp | locus-map | Locus PC-Interface Net Map Server |
126/tcp, udp | unitary | Unisys Unitary Login |
127/tcp, udp | locus-con | Locus PC-Interface Conn Server |
128/tcp, udp | gss-xlicen | GSS X License Verification |
129/tcp, udp | pwdgen | Password Generator Protocol |
130/tcp, udp | cisco-fna | Cisco FNATIVE |
131/tcp, udp | cisco-tna | Cisco TNATIVE |
132/tcp, udp | cisco-sys | Cisco SYSMAINT |
133/tcp, udp | statsrv | Statistics Service |
134/tcp, udp | ingres-net | INGRES-NET Service |
135/tcp, udp | loc-srv | Location Service |
136/tcp, udp | profile | PROFILE Naming System |
137/tcp, udp | netbios-ns | NetBIOS Name Service |
138/tcp, udp | netbios-dgm | NetBIOS Datagram Service |
139/tcp, udp | netbios-ssn | NetBIOS Session Service |
140/tcp, udp | emfis-data | EMFIS Data Service |
141/tcp, udp | emfis-cntl | EMFIS Control Service |
142/tcp, udp | bl-idm | Britton-Lee IDM |
143/tcp, udp | imap2 | Interim Mail Access Protocol v2 |
144/tcp, udp | news | NewS; alias=news |
145/tcp, udp | uaac | UAAC Protocol |
146/tcp, udp | iso-ip0 | ISO-IP0 |
147/tcp, udp | iso-ip | ISO-IP |
148/tcp, udp | cronus | CRONUS-SUPPORT |
149/tcp, udp | aed-512 | AED 512 Emulation Service |
150/tcp, udp | sql-net | SQL-NET |
151/tcp, udp | hems | HEMS |
152/tcp, udp | bftp | Background File Transfer Program |
153/tcp, udp | sgmp | SGMP; alias=sgmp |
154/tcp, udp | netsc-prod | Netscape |
155/tcp, udp | netsc-dev | Netscape |
156/tcp, udp | sqlsrv | SQL Service |
157/tcp, udp | knet-cmp | KNET/VM Command/Message Protocol |
158/tcp, udp | pcmail-srv | PCMail Server; alias=repository |
159/tcp, udp | nss-routing | NSS-Routing |
160/tcp, udp | sgmp-traps | SGMP-TRAPS |
161/tcp, udp | snmp | SNMP; alias=snmp |
162/tcp, udp | snmptrap | SNMPTRAP |
163/tcp, udp | cmip-man | CMIP/TCP Manager |
164/tcp, udp | cmip-agent | CMIP/TCP Agent |
165/tcp, udp | xns-courier | Xerox |
166/tcp, udp | s-net | Sirius Systems |
167/tcp, udp | namp | NAMP |
168/tcp, udp | rsvd | RSVD |
169/tcp, udp | send | SEND |
170/tcp, udp | print-srv | Network PostScript |
171/tcp, udp | multiplex | Network Innovations Multiplex |
172/tcp, udp | cl/1 | Network Innovations CL/1 |
173/tcp, udp | xyplex-mux | Xyplex |
174/tcp, udp | mailq | MAILQ |
175/tcp, udp | vmnet | VMNET |
176/tcp, udp | genrad-mux | GENRAD-MUX |
177/tcp, udp | xdmcp | X Display Manager Control Protocol |
178/tcp, udp | nextstep | NextStep Window Server |
179/tcp, udp | bgp | Border Gateway Protocol |
180/tcp, udp | ris | Intergraph |
181/tcp, udp | unify | Unify |
182/tcp, udp | audit | Unisys Audit SITP |
183/tcp, udp | ocbinder | OCBinder |
184/tcp, udp | ocserver | OCServer |
185/tcp, udp | remote-kis | Remote-KIS |
186/tcp, udp | kis | KIS Protocol |
187/tcp, udp | aci | Application Communication Interface |
188/tcp, udp | mumps | Plus Five's MUMPS |
189/tcp, udp | qft | Queued File Transport |
190/tcp, udp | gacp | Gateway Access Control Protocol |
191/tcp, udp | prospero | Prospero |
192/tcp, udp | osu-nms | OSU Network Monitoring System |
193/tcp, udp | srmp | Spider Remote Monitoring Protocol |
194/tcp, udp | irc | Internet Relay Chat Protocol |
195/tcp, udp | dn6-nlm-aud | DNSIX Network Level Module Audit |
196/tcp, udp | dn6-smm-red | DNSIX Session Mgt Module Audit Redir |
197/tcp, udp | dls | Directory Location Service |
198/tcp, udp | dls-mon | Directory Location Service Monitor |
199/tcp, udp | smux | SMUX |
200/tcp, udp | src | IBM System Resource Controller |
201/tcp, udp | at-rtmp | AppleTalk Routing Maintenance |
202/tcp, udp | at-nbp | AppleTalk Name Binding |
203/tcp, udp | at-3 | AppleTalk Unused |
204/tcp, udp | at-echo | AppleTalk Echo |
205/tcp, udp | at-5 | AppleTalk Unused |
206/tcp, udp | at-zis | AppleTalk Zone Information |
207/tcp, udp | at-7 | AppleTalk Unused |
208/tcp, udp | at-8 | AppleTalk Unused |
209/tcp, udp | tam | Trivial Authenticated Mail Protocol |
210/tcp, udp | z39.50 | ANSI Z39.50 |
211/tcp, udp | 914c/g | Texas Instruments 914C/G Terminal |
212/tcp, udp | anet | ATEXSSTR |
213/tcp, udp | ipx | IPX |
214/tcp, udp | vmpwscs | VM PWSCS |
215/tcp, udp | softpc | Insignia Solutions |
216/tcp, udp | atls | Access Technology License Server |
217/tcp, udp | dbase | dBASE UNIX |
218/tcp, udp | mpp | Netix Message Posting Protocol |
219/tcp, udp | uarps | Unisys ARPs |
220/tcp, udp | imap3 | Interactive Mail Access Protocol v3 |
221/tcp, udp | fln-spx | Berkeley rlogind with SPX auth |
222/tcp, udp | fsh-spx | Berkeley rshd with SPX auth |
223/tcp, udp | cdc | Certificate Distribution Center |
224-241 | Reserved | |
243/tcp, udp | sur-meas | Survey Measurement |
245/tcp, udp | link | LINK |
246/tcp, udp | dsp3270 | Display Systems Protocol |
247-255 | Reserved | |
345/tcp, udp | pawserv | Perf Analysis Workbench |
346/tcp, udp | zserv | Zebra server |
347/tcp, udp | fatserv | Fatmen Server |
371/tcp, udp | clearcase | Clearcase |
372/tcp, udp | ulistserv | UNIX Listserv |
373/tcp, udp | legent-1 | Legent Corporation |
374/tcp, udp | legent-2 | Legent Corporation |
512/tcp | Windows NT Server and Windows NT Workstation version 4.0 can send LPD client print jobs from any available reserved port between 512 and 1023. See also description for ports 721 to 731. | |
512/udp | biff | Used by mail system to notify users of new mail received; currently receives messages only from processes on the same computer; alias=comsat |
513/tcp | login | Remote logon like telnet; automatic authentication performed, based on privileged port numbers and distributed databases that identify "authentication domains" |
513/udp | who | Maintains databases showing who's logged on to the computers on a local net and the load average of the computer; alias=whod |
514/tcp | cmd | Like exec, but automatic authentication is performed as for logon server |
514/udp | syslog | |
515/tcp, udp | printer | Spooler; alias=spooler. The print server LPD service will listen on tcp port 515 for incoming connections. |
517/tcp, udp | talk | Like tenex link, but across computers; unfortunately, doesn't use link protocol (this is actually just a rendezvous port from which a TCP connection is established) |
518/tcp, udp | ntalk | |
519/tcp, udp | utime | Unixtime |
520/tcp | efs | Extended file name server |
520/udp | router | Local routing process (on site); uses variant of Xerox NS routing information protocol;alias=router routed |
525/tcp, udp | timed | Timeserver |
526/tcp, udp | tempo | Newdate |
530/tcp, udp | courier | RPC |
531/tcp | conference | Chat |
531/udp | rvd-control | MIT disk |
532/tcp, udp | netnews | Readnews |
533/tcp, udp | netwall | For emergency broadcasts |
540/tcp, udp | uucp | Uucpd |
543/tcp, udp | klogin | |
544/tcp, udp | kshell | Krcmd; alias=cmd |
550/tcp, udp | new-rwho | New-who |
555/tcp, udp | dsf | |
556/tcp, udp | remotefs | Rfs server; alias=rfs_server rfs |
560/tcp, udp | rmonitor | Rmonitord |
561/tcp, udp | monitor | |
562/tcp, udp | chshell | Chcmd |
564/tcp, udp | 9pfs | Plan 9 file service |
565/tcp, udp | whoami | Whoami |
570/tcp, udp | meter | Demon |
571/tcp, udp | meter | Udemon |
600/tcp, udp | ipcserver | Sun IPC server |
607/tcp, udp | nqs | Nqs |
666/tcp, udp | mdqs | |
704/tcp, udp | elcsd | Errlog copy/server daemon |
721-731/tcp | printer | Under Windows NT 3.5x, all TCP/IP print jobs sent from a Windows NT computer were sourced from TCP ports 721 through 731. This is changed for Windows NT Server and Windows NT Workstation version 4.0, which sources LPD client print jobs from any available reserved port between 512 and 1023. |
740/tcp, udp | netcp | NETscout Control Protocol |
741/tcp, udp | netgw | NetGW |
742/tcp, udp | netrcs | Network based Rev. Cont. Sys. |
744/tcp, udp | flexlm | Flexible License Manager |
747/tcp, udp | fujitsu-dev | Fujitsu Device Control |
748/tcp, udp | ris-cm | Russell Info Sci Calendar Manager |
749/tcp, udp | kerberos-adm | Kerberos administration |
750/tcp | rfile | Kerberos authentication; alias=kdc |
750/udp | loadav | |
751/tcp, udp | pump | Kerberos authentication |
752/tcp, udp | qrh | Kerberos password server |
753/tcp, udp | rrh | Kerberos userreg server |
754/tcp, udp | tell | Send; Kerberos slave propagation |
758/tcp, udp | nlogin | |
759/tcp, udp | con | |
760/tcp, udp | ns | |
761/tcp, udp | rxe | |
762/tcp, udp | quotad | |
763/tcp, udp | cycleserv | |
764/tcp, udp | omserv | |
765/tcp, udp | webster | |
767/tcp, udp | phonebook | Phone |
769/tcp, udp | vid | |
770/tcp, udp | cadlock | |
771/tcp, udp | rtip | |
772/tcp, udp | cycleserv2 | |
773/tcp | submit | |
773/udp | notify | |
774/tcp | rpasswd | |
774/udp | acmaint_dbd | |
775/tcp | entomb | |
775/udp | acmaint_transd | |
776/tcp, udp | wpages | |
780/tcp, udp | wpgs | |
781/tcp, udp | hp-collector | HP performance data collector |
782/tcp, udp | hp-managed-node | HP performance data managed node |
783/tcp, udp | hp-alarm-mgr | HP performance data alarm manager |
800/tcp, udp | mdbs_daemon | |
801/tcp, udp | device | |
888/tcp | erlogin | Logon and environment passing |
996/tcp, udp | xtreelic | XTREE License Server |
997/tcp, udp | maitrd | |
998/tcp | busboy | |
998/udp | puparp | |
999/tcp | garcon | |
999/udp | applix | Applix ac |
999/tcp, udp | puprouter | |
1000/tcp | cadlock | |
1000/udp | ock | |