Port 256RAP

RAP is an obscure service assigned to TCP and UDP port 256, with little evidence of widespread deployment.

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

1 other service is registered on port 256. compare all 2 →

Technical Details

what runs on :256

RAP is registered on port :256 over tcp and udp to J S Greenfield. 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 :256

this machine

# linux
sudo ss -tulpn 'sport = :256'

# macos / bsd
sudo lsof -nP -i :256

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :256

another host

nmap -sV -p T:256 <host>
sudo nmap -sU -sV -p U:256 <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 :256

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 :256 yet

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

Record

iana registry entry

port: :256
service: RAP
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: uncategorised
usage: The IANA registry assigns the RAP service on TCP and UDP port 256 to J S Greenfield. No public protocol or product context is recorded, and the port is rarely observed open on the internet.
lookups: 0rank 993
added: 2026-08-23
updated: 2026-08-23
references: IANA service name registry — port 256

Something wrong?

This record is maintained by the engineers who use port 256. 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 2026-08-23.

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 :256, by lookups.

port	service	proto	category	risk	views
:311	Mac OS X Server Admin	TCP	Web Services	caution	23.7k
:201	AppleTalk Routing	TCPUDP	Network Services	caution	19.7k
:194	Internet Relay Chat	TCPUDP	Voice and Chat	caution	17.5k
:213	IPX	TCPUDP	Network Services	caution	13.9k
:264	Border Gateway Multicast Protocol	TCPUDP	Network Services	caution	12.2k
:210	ANSI Z39.50	TCPUDP	Databases	caution	9.0k
:199	SMUX (SNMP Multiplexer)	TCPUDP	Network Services	caution	9.0k
:220	IMAP v3	TCPUDP	Email	caution	8.6k

risk mix of the 8 listed

caution100%

0 of 8 encrypted

Port :256RAP

Technical Details

Security Information

Related Ports

Port 256RAP