Port 3933PL/B App Server User Port

TCP and UDP 3933 are assigned to the PL/B App Server User Port, an obscure service with no established public use.

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

also known as plbserve-port

Technical Details

what runs on :3933

PL/B App Server User Port is registered on port :3933 over tcp and udp to Edward R Boedecker, assigned November 2003. 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 :3933

this machine

# linux
sudo ss -tulpn 'sport = :3933'

# macos / bsd
sudo lsof -nP -i :3933

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :3933

another host

nmap -sV -p T:3933 <host>
sudo nmap -sU -sV -p U:3933 <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 :3933

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 :3933 yet

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

Record

iana registry entry

port: :3933
service: PL/B App Server User Port
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: uncategorised
usage: IANA labels TCP and UDP 3933 as the PL/B App Server User Port and lists Edward R Boedecker as the registrant. It is not a commonly encountered public service.
lookups: 0rank 993
added: 2026-10-02
updated: 2026-10-02
references: IANA service name registry — port 3933

Something wrong?

This record is maintained by the engineers who use port 3933. 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 2026-10-02.

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 :3933, by lookups.

port	service	proto	category	risk	views
:3899	Remote Administrator	TCP	Remote Access	caution	20.6k
:3872	Oracle Management Agent	TCP	Databases	caution	14.3k
:3978	OpenTTD Master Server	TCPUDP	Gaming	caution	12.5k
:3945	EMCADS	TCPUDP	Security	caution	7.6k
:3900	IBM UniData UDT OS	TCP	Databases	caution	6.4k
:3880	IGRS	TCPUDP	Network Services	caution	5.2k
:3979	OpenTTD	TCPUDP	Gaming	caution	4.4k
:3947	Connect and Control Protocol (CCP)	TCPUDP	IoT	safe	0

risk mix of the 8 listed

safe13%
caution88%

0 of 8 encrypted

Port :3933PL/B App Server User Port

Technical Details

Security Information

Related Ports

Port 3933PL/B App Server User Port