Port 4099DPCP

DPCP is an obscure service-port assignment with no established public protocol or common deployment.

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

Technical Details

what runs on :4099

DPCP is registered on port :4099 over tcp and udp to John Croft. 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 :4099

this machine

# linux
sudo ss -tulpn 'sport = :4099'

# macos / bsd
sudo lsof -nP -i :4099

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :4099

another host

nmap -sV -p T:4099 <host>
sudo nmap -sU -sV -p U:4099 <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 :4099

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 :4099 yet

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

Record

iana registry entry

port: :4099
service: DPCP
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: uncategorised
usage: IANA lists TCP and UDP port 4099 as DPCP, registered to John Croft; the registration date is not recorded. No common public implementation is established, and the port has not appeared open in the cited Nmap scan data.
lookups: 0rank 993
added: 2026-10-03
updated: 2026-10-03
references: IANA service name registry — port 4099

Something wrong?

This record is maintained by the engineers who use port 4099. 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 2026-10-03.

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 :4099, by lookups.

port	service	proto	category	risk	views
:4125	Remote Web Workplace	TCP	Web Services	caution	20.5k
:4096	Ascom Timeplex BRE	TCPUDP	Network Services	safe	16.5k
:4116	Smartcard TLS	TCPUDP	Security	caution	13.6k
:4100	WatchGuard Auth Applet		Security	caution	10.1k
:4069	Minger Email Verification	UDP	Email	caution	8.5k
:4093	PxPlus Client Server	TCPUDP	Databases	caution	8.0k
:4111	Xgrid	TCP	System	caution	7.4k
:4089	OpenCORE Remote Control	TCPUDP	Remote Access	caution	7.4k

risk mix of the 8 listed

safe13%
caution88%

0 of 8 encrypted

Port :4099DPCP

Technical Details

Security Information

Related Ports

Port 4099DPCP