Port 1721caicci

The caicci service assignment on TCP and UDP port 1721; public protocol details are not recorded.

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

Technical Details

what runs on :1721

caicci is registered on port :1721 over tcp and udp to Sylvia Scheuren. 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 found open rarely. What's listening is often not the registered service, so check before you assume.

find what's listening on :1721

this machine

# linux
sudo ss -tulpn 'sport = :1721'

# macos / bsd
sudo lsof -nP -i :1721

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :1721

another host

nmap -sV -p T:1721 <host>
sudo nmap -sU -sV -p U:1721 <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 :1721

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 :1721 yet

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

Record

iana registry entry

port: :1721
service: caicci
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: uncategorised
usage: caicci is an IANA-assigned service name for TCP and UDP port 1721, registered to Sylvia Scheuren. No protocol specification or usage guidance is recorded, and the port is rarely observed open.
lookups: 0rank 993
added: 2026-09-09
updated: 2026-09-09
references: IANA service name registry — port 1721

Something wrong?

This record is maintained by the engineers who use port 1721. 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 2026-09-09.

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 :1721, by lookups.

port	service	proto	category	risk	views
:1720	H.323 Signaling	TCP	Network Services	caution	26.5k
:1701	L2TP & L2F	UDP	Security	caution	15.1k
:1755	Microsoft Media Services	TCPUDP	Streaming	caution	13.8k
:1716	America's Army MMO	TCP	Network Services	caution	12.6k
:1723	PPTP	TCPUDP	Security	caution	11.3k
:1719	H.323 RAS	UDP	Network Services	caution	9.2k
:1677	Novell GroupWise	TCPUDP	Email	caution	7.5k
:1725	Valve Steam	UDP	Gaming	caution	7.3k

risk mix of the 8 listed

caution100%

0 of 8 encrypted

Port :1721caicci

Technical Details

Security Information

Related Ports

Port 1721caicci