Internet Assigned Numbers Authority

Service Name and Transport Protocol Port Number Registry

Last Updated
2025-08-15
Expert(s)
TCP/UDP: Joe Touch; Eliot Lear, Kumiko Ono, Wes Eddy, Brian Trammell, 
Jana Iyengar, and Michael Scharf
SCTP: Michael Tuexen
DCCP: Eddie Kohler and Yoshifumi Nishida
Reference
[RFC6335]
Note
Service names and port numbers are used to distinguish between different
services that run over transport protocols such as TCP, UDP, DCCP, and
SCTP.

Service names are assigned on a first-come, first-served process, as
documented in [RFC6335].

Port numbers are assigned in various ways, based on three ranges: System
Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private
Ports (49152-65535); the different uses of these ranges are described in
[RFC6335]. According to Section 8.1.2 of [RFC6335], System Ports are 
assigned by the "IETF Review" or "IESG Approval" procedures described in 
[RFC8126]. User Ports are assigned by IANA using the "IETF Review" process, 
the "IESG Approval" process, or the "Expert Review" process, as per 
[RFC6335]. Dynamic Ports are not assigned.

The registration procedures for service names and port numbers are
described in [RFC6335].

Assigned ports both System and User ports SHOULD NOT be used without
or prior to IANA registration.

************************************************************************
* PLEASE NOTE THE FOLLOWING:                                           *
*                                                                      *
* ASSIGNMENT OF A PORT NUMBER DOES NOT IN ANY WAY IMPLY AN             *
* ENDORSEMENT OF AN APPLICATION OR PRODUCT, AND THE FACT THAT NETWORK  *
* TRAFFIC IS FLOWING TO OR FROM A REGISTERED PORT DOES NOT MEAN THAT   *
* IT IS "GOOD" TRAFFIC, NOR THAT IT NECESSARILY CORRESPONDS TO THE     *
* ASSIGNED SERVICE. FIREWALL AND SYSTEM ADMINISTRATORS SHOULD          *
* CHOOSE HOW TO CONFIGURE THEIR SYSTEMS BASED ON THEIR KNOWLEDGE OF    *
* THE TRAFFIC IN QUESTION, NOT WHETHER THERE IS A PORT NUMBER          *
* REGISTERED OR NOT.                                                   *
************************************************************************

Request an Assignment
  [https://www.iana.org/protocols/apply]

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Service Name Port Number Transport Protocol Description Assignee Contact Registration Date Modification Date Reference Service Code Unauthorized Use Reported Assignment Notes
0 tcp Reserved 2024-12-20 [RFC6335]
0 udp Reserved 2024-12-20 [RFC6335]
2 tcp Reserved 2025-02-13 De-assigned on 2025-02-13, previously compressnet by [Bernie_Volz]
2 udp Reserved 2025-02-13 De-assigned on 2025-02-13, previously compressnet by [Bernie_Volz]
3 tcp Reserved 2025-02-13 De-assigned on 2025-02-13, previously compressnet by [Bernie_Volz]
3 udp Reserved 2025-02-13 De-assigned on 2025-02-13, previously compressnet by [Bernie_Volz]
rje 5 tcp Remote Job Entry [Jon_Postel] [Jon_Postel]
rje 5 udp Remote Job Entry [Jon_Postel] [Jon_Postel]
discard 9 dccp Discard [Eddie_Kohler] [Eddie_Kohler] [RFC4340] 1145656131
15 tcp Unassigned [was netstat]
15 udp Unassigned
ftp 21 tcp File Transfer Protocol [Control] [Jon_Postel] [Jon_Postel] [RFC959] Defined TXT keys: u=<username> p=<password> path=<path>
ftp 21 udp File Transfer Protocol [Control] [Jon_Postel] [Jon_Postel] [RFC959] Defined TXT keys: u=<username> p=<password> path=<path>
ssh 22 tcp The Secure Shell (SSH) Protocol [RFC4251] Defined TXT keys: u=<username> p=<password>
ssh 22 udp The Secure Shell (SSH) Protocol [RFC4251] Defined TXT keys: u=<username> p=<password>
telnet 23 tcp Telnet [Jon_Postel] [Jon_Postel] [RFC854] Defined TXT keys: u=<username> p=<password>
telnet 23 udp Telnet [Jon_Postel] [Jon_Postel] [RFC854] Defined TXT keys: u=<username> p=<password>
smtp 25 tcp Simple Mail Transfer [IESG] [IETF_Chair] 2017-06-05 [RFC-ietf-emailcore-rfc5321bis-43]
smtp 25 udp Simple Mail Transfer [IESG] [IETF_Chair] 2017-06-05 [RFC-ietf-emailcore-rfc5321bis-43]
35 tcp any private printer server [Jon_Postel] [Jon_Postel]
35 udp any private printer server [Jon_Postel] [Jon_Postel]
mpm 45 tcp Message Processing Module [recv]
mpm 45 udp Message Processing Module [recv]
47 tcp Reserved 2017-05-18 This entry has been removed on 2017-05-18.
47 udp Reserved 2017-05-18 This entry has been removed on 2017-05-18.
re-mail-ck 50 tcp Remote Mail Checking Protocol [Steve_Dorner] [Steve_Dorner]
re-mail-ck 50 udp Remote Mail Checking Protocol [Steve_Dorner] [Steve_Dorner]
51 Reserved 2013-05-24 This entry is being removed on 2013-05-24.
xns-time 52 tcp XNS Time Protocol [Susie_Armstrong] [Susie_Armstrong]
xns-time 52 udp XNS Time Protocol [Susie_Armstrong] [Susie_Armstrong]
domain 53 tcp Domain Name Server [Paul_Mockapetris] [Paul_Mockapetris]
domain 53 udp Domain Name Server [Paul_Mockapetris] [Paul_Mockapetris]
xns-ch 54 tcp XNS Clearinghouse [Susie_Armstrong] [Susie_Armstrong]
xns-ch 54 udp XNS Clearinghouse [Susie_Armstrong] [Susie_Armstrong]
isi-gl 55 tcp ISI Graphics Language
isi-gl 55 udp ISI Graphics Language
xns-auth 56 tcp XNS Authentication [Susie_Armstrong] [Susie_Armstrong]
xns-auth 56 udp XNS Authentication [Susie_Armstrong] [Susie_Armstrong]
57 tcp any private terminal access [Jon_Postel] [Jon_Postel]
57 udp any private terminal access [Jon_Postel] [Jon_Postel]
xns-mail 58 tcp XNS Mail [Susie_Armstrong] [Susie_Armstrong]
xns-mail 58 udp XNS Mail [Susie_Armstrong] [Susie_Armstrong]
59 tcp any private file service [Jon_Postel] [Jon_Postel]
59 udp any private file service [Jon_Postel] [Jon_Postel]
61 tcp Reserved 2017-05-18 This entry has been removed on 2017-05-18.
61 udp Reserved 2017-05-18 This entry has been removed on 2017-05-18.
tacacs-ds 65 tcp TACACS-Database Service [Kathy_Huber] [Kathy_Huber]
tacacs-ds 65 udp TACACS-Database Service [Kathy_Huber] [Kathy_Huber]
bootps 67 tcp Bootstrap Protocol Server [Bill_Croft] [Bill_Croft] [RFC951] Defined TXT keys: None
75 tcp any private dial out service [Jon_Postel] [Jon_Postel]
75 udp any private dial out service [Jon_Postel] [Jon_Postel]
mit-ml-dev 85 tcp MIT ML Device [David_Reed] [David_Reed]
mit-ml-dev 85 udp MIT ML Device [David_Reed] [David_Reed]
supdup 95 tcp SUPDUP [Mark_Crispin] [Mark_Crispin]
supdup 95 udp SUPDUP [Mark_Crispin] [Mark_Crispin]
cso 105 tcp CCSO name server protocol [Martin_Hamilton] [Martin_Hamilton]
cso 105 udp CCSO name server protocol [Martin_Hamilton] [Martin_Hamilton]
csnet-ns 105 tcp Mailbox Name Nameserver [Marvin_Solomon] [Marvin_Solomon]
csnet-ns 105 udp Mailbox Name Nameserver [Marvin_Solomon] [Marvin_Solomon]
sftp 115 tcp Simple File Transfer Protocol [Mark_Lottor] [Mark_Lottor]
sftp 115 udp Simple File Transfer Protocol [Mark_Lottor] [Mark_Lottor]
ntp 123 tcp Network Time Protocol [Dave_Mills] [Dave_Mills] [RFC5905]
ntp 123 udp Network Time Protocol [Dave_Mills] [Dave_Mills] [RFC5905]
locus-map 125 tcp Locus PC-Interface Net Map Ser [Eric_Peterson] [Eric_Peterson]
locus-map 125 udp Locus PC-Interface Net Map Ser [Eric_Peterson] [Eric_Peterson]
epmap 135 tcp DCE endpoint resolution [Joe_Pato] [Joe_Pato]
epmap 135 udp DCE endpoint resolution [Joe_Pato] [Joe_Pato]
imap 143 tcp Internet Message Access Protocol [IESG] [IETF_Chair] 2021-02-22 [RFC3501][RFC9051]
143 udp Reserved 2021-02-22 [RFC9051]
uaac 145 tcp UAAC Protocol [David_A_Gomberg] [David_A_Gomberg]
uaac 145 udp UAAC Protocol [David_A_Gomberg] [David_A_Gomberg]
aed-512 149 tcp AED 512 Emulation Service [Albert_G_Broscius] [Albert_G_Broscius]
aed-512 149 udp AED 512 Emulation Service [Albert_G_Broscius] [Albert_G_Broscius]
sql-net 150 tcp SQL-NET [Martin_Picard] [Martin_Picard]
sql-net 150 udp SQL-NET [Martin_Picard] [Martin_Picard]
hems 151 tcp HEMS
hems 151 udp HEMS
bftp 152 tcp Background File Transfer Program [Annette_DeSchon] [Annette_DeSchon]
bftp 152 udp Background File Transfer Program [Annette_DeSchon] [Annette_DeSchon]
sgmp 153 tcp SGMP [Marty_Schoffstahl] [Marty_Schoffstahl]
sgmp 153 udp SGMP [Marty_Schoffstahl] [Marty_Schoffstahl]
netsc-prod 154 tcp NETSC
netsc-prod 154 udp NETSC
netsc-dev 155 tcp NETSC [Sergio_Heker] [Sergio_Heker]
netsc-dev 155 udp NETSC [Sergio_Heker] [Sergio_Heker]
sqlsrv 156 tcp SQL Service [Craig_Rogers] [Craig_Rogers]
sqlsrv 156 udp SQL Service [Craig_Rogers] [Craig_Rogers]
knet-cmp 157 tcp KNET/VM Command/Message Protocol [Gary_S_Malkin] [Gary_S_Malkin]
knet-cmp 157 udp KNET/VM Command/Message Protocol [Gary_S_Malkin] [Gary_S_Malkin]
pcmail-srv 158 tcp PCMail Server [Mark_L_Lambert] [Mark_L_Lambert]
pcmail-srv 158 udp PCMail Server [Mark_L_Lambert] [Mark_L_Lambert]
nss-routing 159 tcp NSS-Routing [Yakov_Rekhter] [Yakov_Rekhter]
nss-routing 159 udp NSS-Routing [Yakov_Rekhter] [Yakov_Rekhter]
xns-courier 165 tcp Xerox [Susie_Armstrong_2] [Susie_Armstrong_2]
xns-courier 165 udp Xerox [Susie_Armstrong_2] [Susie_Armstrong_2]
vmnet 175 tcp VMNET [Christopher_Tengi] [Christopher_Tengi]
vmnet 175 udp VMNET [Christopher_Tengi] [Christopher_Tengi]
remote-kis 185 tcp Remote-KIS
remote-kis 185 udp Remote-KIS
dn6-nlm-aud 195 tcp DNSIX Network Level Module Audit

Contact Information

ID Name Organization Contact URI Last Updated
[Albert_G_Broscius] Albert G. Broscius mailto:broscius&dsl.cis.upenn.edu
[Annette_DeSchon] Annette DeSchon mailto:DESCHON&isi.edu
[Bernie_Volz] Bernie Volz mailto:volz&cisco.com
[Bill_Croft] Bill Croft mailto:Croft&sumex-aim.stanford.edu
[Christopher_Tengi] Christopher Tengi mailto:tengi&princeton.edu
[Craig_Rogers] Craig Rogers mailto:Rogers&isi.edu
[Dave_Mills] Dave Mills mailto:mills&udel.edu 2022-06-03
[David_A_Gomberg] David A. Gomberg mailto:gomberg&gateway.mitre.org
[David_Reed] David Reed
[Eddie_Kohler] Eddie Kohler IETF dccp WG mailto:kohler&cs.ucla.edu
[Eric_Peterson] Eric Peterson mailto:lcc.eric&seas.ucla.edu
[Gary_S_Malkin] Gary S. Malkin mailto:GMALKIN&xylogics.com
[IESG] IESG mailto:iesg&ietf.org
[IETF_Chair] IETF Chair IETF mailto:chair&ietf.org
[Joe_Pato] Joe Pato mailto:pato&apollo.hp.com
[Jon_Postel] Jon Postel mailto:postel&isi.edu
[Kathy_Huber] Kathy Huber mailto:khuber&bbn.com
[Mark_Crispin] Mark Crispin mailto:MRC&panda.com
[Mark_L_Lambert] Mark L. Lambert mailto:markl&ptt.lcs.mit.edu
[Mark_Lottor] Mark Lottor mailto:MKL&nisc.sri.com
[Martin_Hamilton] Martin Hamilton mailto:martin&mrrl.lut.as.uk
[Martin_Picard] Martin Picard
[Marty_Schoffstahl] Marty Schoffstahl mailto:schoff&nisc.nyser.net
[Marvin_Solomon] Marvin Solomon mailto:solomon&cs.wisc.edu
[Paul_Mockapetris] Paul Mockapetris mailto:PVM&isi.edu
[Sergio_Heker] Sergio Heker mailto:heker&jvncc.csc.org
[Steve_Dorner] Steve Dorner mailto:s-dorner&uiuc.edu
[Susie_Armstrong] Susie Armstrong mailto:Armstrong.wbst128@xerox
[Susie_Armstrong_2] Susie Armstrong mailto:Armstrong.wbst128&xerox.com
[Yakov_Rekhter] Yakov Rekhter mailto:Yakov&ibm.com