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// Other services

Port 9951: APC 9951

Port 9951 is assigned by IANA to apc-9951 (APC 9951).

9951

How apc-9951 works

Other services
client:9951apc-9951response client:9951apc-9951response

The client sends a request to port 9951 and the apc-9951 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 9951 dangerous?

We have no specific security note for port 9951. 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 9951

ServicePortTransportDescriptionReferenceUpdated
apc-9951 9951 TCP, UDP APC 9951 - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 9951, and is it reachable?

Linux

sudo ss -ltnup 'sport = :9951'      # process listening on 9951
sudo lsof -nP -i :9951

macOS

sudo lsof -nP -i :9951

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9951 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 9951
netstat -ano | findstr :9951

From another machine

nmap -p 9951 -sV <host>
sudo nmap -sU -p 9951 <host>
nc -zv <host> 9951

Block it in the firewall

sudo ufw deny 9951/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 9951" -Direction Inbound -LocalPort 9951 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 9951 used for?

Port 9951 is assigned by IANA to apc-9951 (APC 9951).

Is port 9951 TCP or UDP?

Port 9951 is registered for TCP and UDP.

Is it safe to open port 9951?

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 9951 is open?

On Linux run "ss -ltnup 'sport = :9951'", on macOS "lsof -nP -i :9951", and on Windows "netstat -ano | findstr :9951" to see the local process. From another machine, "nmap -p 9951 <host>" shows whether it is reachable.

05 Related
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