Port 3331MCS Messaging

MCS Messaging is assigned to TCP and UDP port 3331 for an unspecified messaging service.

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

Technical Details

what runs on :3331

MCS Messaging is registered on port :3331 over tcp and udp. 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 :3331

this machine

# linux
sudo ss -tulpn 'sport = :3331'

# macos / bsd
sudo lsof -nP -i :3331

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :3331

another host

nmap -sV -p T:3331 <host>
sudo nmap -sU -sV -p U:3331 <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 :3331

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 :3331 yet

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

Record

iana registry entry

port: :3331
service: MCS Messaging
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: uncategorised
usage: The IANA registry identifies TCP and UDP port 3331 as MCS Messaging. No registrant or public protocol details are recorded, so deployments cannot be identified from the assignment alone.
lookups: 0rank 993
added: 2026-09-04
updated: 2026-09-04
references: IANA service name registry — port 3331

Something wrong?

This record is maintained by the engineers who use port 3331. 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 2026-09-04.

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 :3331, by lookups.

port	service	proto	category	risk	views
:3268	Microsoft Global Catalog (GC)	TCPUDP	Security	caution	54.6k
:3269	Microsoft Global Catalog SSL	TCPUDPtls	Security	caution	26.4k
:3283	Apple Remote Desktop Reporting	TCP	Remote Access	caution	26.0k
:3386	GTP (GPRS Tunneling Protocol)	TCPUDP	Network Services	caution	16.7k
:3389	Microsoft RDP	TCPUDP	Remote Access	caution	16.3k
:3299	SAP Router	TCPtls	Network Services	caution	13.8k
:3306	MySQL	TCPUDP	Databases	caution	13.6k
:3333	Network Caller ID	TCP	Network Services	caution	10.1k

risk mix of the 8 listed

caution100%

2 of 8 encrypted

Port :3331MCS Messaging

Technical Details

Security Information

Related Ports

Port 3331MCS Messaging