Port 22003Opto Host Port 3

TCP and UDP port 22003 is assigned to Opto Host Port 3, a service with no widely documented implementation.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 1/10
lookups: 0

also known as optohost003

Technical Details

what runs on :22003

Opto Host Port 3 is registered on port :22003 over tcp and udp to Doug Leany, assigned September 2006. We don't have a technical write-up for it beyond the IANA registry entry.

In nmap's internet-wide scan data this port is never observed open, so if it's open on your network it's more likely a custom or misconfigured service than the registered one.

find what's listening on :22003

this machine

# linux
sudo ss -tulpn 'sport = :22003'

# macos / bsd
sudo lsof -nP -i :22003

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :22003

another host

nmap -sV -p T:22003 <host>
sudo nmap -sU -sV -p U:22003 <host>

run it? the handshake, the implementations you meet in the wild and the flags that matter come from the engineers who do.

add technical details

Security Information

exposure of :22003

risk score

1/ 10safe

routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

no security notes recorded for :22003 yet

known exploits, hardening advice, what a compromise looks like — suggest an edit if you know its exposure.

Record

iana registry entry

port: :22003
service: Opto Host Port 3
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: uncategorised
usage: IANA assigns TCP and UDP port 22003 to Opto Host Port 3. The assignment is registered to Doug Leany; no common deployment is documented, and it has not appeared open in Nmap's scan data.
lookups: 0rank 993
added: 2026-10-18
updated: 2026-10-18
references: IANA service name registry — port 22003

Something wrong?

This record is maintained by the engineers who use port 22003. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-10-18.

01edit any field on a page of its own
02a model checks it for accuracy and spam
03clean and confident goes live immediately

edit this record →back to the registry

Related Ports

browse categories →

ports registered around :22003, by lookups.

port	service	proto	category	risk
:22000	Syncthing	TCPUDPtls	File Transfer	caution
:22001	OptoControl	TCPUDP	—	safe
:22002	Opto Host Port 2	TCPUDP	—	safe
:22004	Opto Host Port 4	TCPUDP	—	safe
:22005	Opto Host Port 5	TCPUDP	—	safe

risk mix of the 5 listed

safe80%
caution20%

1 of 5 encrypted

Port :22003Opto Host Port 3

Technical Details

Security Information

Related Ports

Port 22003Opto Host Port 3