Port 553pirp

An obscure PIRP service assignment held by D. J. Bernstein on TCP and UDP port 553.

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

Technical Details

what runs on :553

pirp is registered on port :553 over tcp and udp to D J Bernstein. 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 :553

this machine

# linux
sudo ss -tulpn 'sport = :553'

# macos / bsd
sudo lsof -nP -i :553

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :553

another host

nmap -sV -p T:553 <host>
sudo nmap -sU -sV -p U:553 <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 :553

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 :553 yet

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

Record

iana registry entry

port: :553
service: pirp
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: uncategorised
usage: IANA assigns the name pirp to TCP and UDP port 553, registered to D. J. Bernstein. The registry provides no expansion, protocol description, deployment guidance, or recorded registration date.
lookups: 0rank 993
added: 2026-08-26
updated: 2026-08-26
references: IANA service name registry — port 553

Something wrong?

This record is maintained by the engineers who use port 553. 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 2026-08-26.

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 :553, by lookups.

port	service	proto	category	risk	views
:548	Apple Filing Protocol	TCP	File Transfer	caution	36.8k
:593	HTTP RPC Endpoint Mapper	TCPUDP	Network Services	caution	26.0k
:591	FileMaker Web Sharing	TCP	Web Services	caution	23.1k
:502	Modbus Protocol	TCPUDP	Network Services	caution	19.2k
:563	NNTPS	TCPUDPtls	Web Services	safe	18.1k
:546	DHCPv6 Client	TCPUDP	Network Services	caution	16.6k
:547	DHCPv6 Server	TCPUDP	Network Services	caution	14.5k
:533	Netwall Emergency Broadcasts	UDP	Security	caution	14.3k

risk mix of the 8 listed

safe13%
caution88%

1 of 8 encrypted

Port :553pirp

Technical Details

Security Information

Related Ports

Port 553pirp