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// Other services

Port 9998: Distinct32

Port 9998 is assigned by IANA to distinct32 (Distinct32).

9998

How distinct32 works

Other services
client:9998distinct32response client:9998distinct32response

The client sends a request to port 9998 and the distinct32 service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Other services
01 Security

Is port 9998 dangerous?

We have no specific security note for port 9998. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 9998

ServicePortTransportDescriptionReferenceUpdated
distinct32 9998 TCP, UDP Distinct32 - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 9998, and is it reachable?

Linux

sudo ss -ltnup 'sport = :9998'      # process listening on 9998
sudo lsof -nP -i :9998

macOS

sudo lsof -nP -i :9998

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9998 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 9998
netstat -ano | findstr :9998

From another machine

nmap -p 9998 -sV <host>
sudo nmap -sU -p 9998 <host>
nc -zv <host> 9998

Block it in the firewall

sudo ufw deny 9998/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 9998" -Direction Inbound -LocalPort 9998 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 9998 used for?

Port 9998 is assigned by IANA to distinct32 (Distinct32).

Is port 9998 TCP or UDP?

Port 9998 is registered for TCP and UDP.

Is it safe to open port 9998?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Close the port if nothing on the host needs it.

How do I check if port 9998 is open?

On Linux run "ss -ltnup 'sport = :9998'", on macOS "lsof -nP -i :9998", and on Windows "netstat -ano | findstr :9998" to see the local process. From another machine, "nmap -p 9998 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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