IANA lists at least one assignment on 38 of the 2,000 numbers from 21000 to 22999, 1.9%. The longest stretch with no assignment on any protocol runs from 21338 to 21552 (215 numbers). 12 numbers here are assigned on TCP alone and 0 on UDP alone. Of the 25 dated assignments, the earliest recorded date is November 2004 (irtrans on 21000); the latest is October 16, 2025, for xahaud on 21337.
One square per number, 21000 at top left. Outlined squares have their own page.TCP and UDPTCP onlyUDP onlySCTP or DCCP onlyno assignment
Every assigned number from 21000 to 22999
21000–21099 · 2 numbers assigned
Port
Service
Protocols
Label
Registered
21000
irtrans
TCPUDP
IRTrans Control
Nov 2004
21010
notezilla-lan
TCP
Notezilla.Lan Server
Aug 20, 2013
21011–21099: no assignment, 89 numbers
21100–21199: no assignment, 100 numbers
21200–21299 · 3 numbers assigned
Port
Service
Protocols
Label
Registered
21200–21211: no assignment, 12 numbers
21212
trinket-agent
TCP
Distributed artificial intelligence
Nov 29, 2017
21213
cohesity-agent
TCP
Cohesity backup agents
Aug 1, 2019
21221
aigairserver
TCP
Services for Air Server
Mar 16, 2017
21222–21299: no assignment, 78 numbers
21300–21399 · 1 number assigned
Port
Service
Protocols
Label
Registered
21300–21336: no assignment, 37 numbers
21337
xahaud
TCP
Xahau P2P network protocol
Oct 16, 2025
21338–21399: no assignment, 62 numbers
21400–21499: no assignment, 100 numbers
21500–21599 · 3 numbers assigned
Port
Service
Protocols
Label
Registered
21500–21552: no assignment, 53 numbers
21553
rdm-tfs
TCP
Raima RDM TFS
May 2, 2011
21554
dfserver
TCPUDP
MineScape Design File Server
Jun 2006
21555–21589: no assignment, 35 numbers
21590
vofr-gateway
TCPUDP
VoFR Gateway
—
21600–21799: no assignment, 200 numbers
21800–21899 · 7 numbers assigned
Port
Service
Protocols
Label
Registered
21800
tvpm
TCPUDP
TVNC Pro Multiplexing
—
21801
sal
TCP
Safe AutoLogon
Jul 5, 2022
21802–21844: no assignment, 43 numbers
21845
webphone
TCPUDP
webphone
—
21846
netspeak-is
TCPUDP
NetSpeak Corp. Directory Services
—
21847
netspeak-cs
TCPUDP
NetSpeak Corp. Connection Services
—
21848
netspeak-acd
TCPUDP
NetSpeak Corp. Automatic Call Distribution
—
21849
netspeak-cps
TCPUDP
NetSpeak Corp. Credit Processing System
—
21850–21899: no assignment, 50 numbers
21900–21999: no assignment, 100 numbers
22000–22099 · 6 numbers assigned
Port
Service
Protocols
Label
Registered
22000
snapenetio
TCPUDP
SNAPenetIO
—
22001
optocontrol
TCPUDP
OptoControl
—
22002
optohost002
TCPUDP
Opto Host Port 2
Sep 2006
22003
optohost003
TCPUDP
Opto Host Port 3
Sep 2006
22004
optohost004
TCPUDP
Opto Host Port 4
Sep 2006
22005
optohost004
TCPUDP
Opto Host Port 5
Sep 2006
22006–22099: no assignment, 94 numbers
22100–22199 · 2 numbers assigned
Port
Service
Protocols
Label
Registered
22100–22124: no assignment, 25 numbers
22125
dcap
TCP
dCache Access Protocol
Mar 10, 2009
22128
gsidcap
TCP
GSI dCache Access Protocol
Mar 10, 2009
22129–22199: no assignment, 71 numbers
22200–22299 · 2 numbers assigned
Port
Service
Protocols
Label
Registered
22200–22221: no assignment, 22 numbers
22222
easyengine
TCP
EasyEngine is CLI tool to manage WordPress Sites on Nginx server
Mar 10, 2014
22223–22272: no assignment, 50 numbers
22273
wnn6
TCPUDP
wnn6
—
22274–22299: no assignment, 26 numbers
22300–22399 · 7 numbers assigned
Port
Service
Protocols
Label
Registered
22305
cis
TCPUDP
CompactIS Tunnel
Aug 16, 2007
22306–22332: no assignment, 27 numbers
22333
showcockpit-net
TCPUDP
ShowCockpit Networking
Nov 18, 2020
22335
shrewd-control shrewd-stream
TCPUDP
Initium Labs Security and Automation Control Initium Labs Security and Automation Streaming
Mar 6, 2015
22343
cis-secure
TCPUDP
CompactIS Secure Tunnel
Aug 16, 2007
22347
wibukey
TCPUDP
WibuKey Standard WkLan
Jun 2007
22350
codemeter
TCPUDP
CodeMeter Standard
Jun 2007
22351
codemeter-cmwan
TCP
TPC/IP requests of copy protection software to a server