Port 4026Graphical Debug Server

Port 4026 is assigned to the Graphical Debug Server service.

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

also known as as-debug

Technical Details

what runs on :4026

Graphical Debug Server is registered on port :4026 over tcp and udp to Steve Halverson. 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 :4026

this machine

# linux
sudo ss -tulpn 'sport = :4026'

# macos / bsd
sudo lsof -nP -i :4026

# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :4026

another host

nmap -sV -p T:4026 <host>
sudo nmap -sU -sV -p U:4026 <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 :4026

risk score

1/ 10safe

routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.

system averages 2.7 across 909 ports — this one sits 1.7 below.

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 :4026 yet

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

Record

iana registry entry

port: :4026
service: Graphical Debug Server
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: System
usage: IANA assigns TCP and UDP port 4026 to the Graphical Debug Server service. The assignment is registered to Steve Halverson, with no additional product or deployment details recorded.
lookups: 0rank 993
added: 2026-09-05
updated: 2026-09-05
references: IANA service name registry — port 4026

Something wrong?

This record is maintained by the engineers who use port 4026. 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 2026-09-05.

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

all 909 in system →

the 8 most looked-up other ports in system — 909 ports carry that label.

port	service	proto	category	risk	views
:8888	Sun Answerbook & Alt HTTP	TCP	Web Services	caution	123.9k
:4664	Google Desktop Search	TCP	System	caution	67.2k
:8008	IBM HTTP Server Admin	TCP	Web Services	caution	58.3k
:3268	Microsoft Global Catalog (GC)	TCPUDP	Security	caution	54.6k
:135	Microsoft EPMAP	TCPUDP	Security	caution	51.9k
:9080	WebSphere HTTP Transport (default)	TCP	Web Services	caution	51.6k
:23	Telnet	TCP	Remote Access	caution	34.8k
:12489	NSClient Monitoring Agent	TCP	Network Services	caution	30.0k

risk mix of the 8 listed

caution100%

0 of 8 encrypted

Port :4026Graphical Debug Server

Technical Details

Security Information

Related Ports

Port 4026Graphical Debug Server