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// Other services

Port 9901: enrp server channel

Port 9901 is assigned by IANA to enrp (enrp server channel), enrp-sctp (enrp server channel).

9901

How enrp works

Other services
client:9901enrpresponse client:9901enrpresponse

The client sends a request to port 9901 and the enrp service answers.

Transport
UDP · SCTP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned2 registered services
Range
Registered (1024-49151)
Category
Other services
01 Security

Is port 9901 dangerous?

We have no specific security note for port 9901. 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 9901

ServicePortTransportDescriptionReferenceUpdated
enrp 9901 UDP enrp server channel - -
enrp-sctp 9901 SCTP enrp server channel RFC 5353 -

// source: IANA service name and port number registry

03 Check it

Which program uses port 9901, and is it reachable?

Linux

sudo ss -ltnup 'sport = :9901'      # process listening on 9901
sudo lsof -nP -i :9901

macOS

sudo lsof -nP -i :9901

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9901 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 9901
netstat -ano | findstr :9901

From another machine

nmap -p 9901 -sV <host>
sudo nmap -sU -p 9901 <host>
nc -zv <host> 9901

Block it in the firewall

sudo ufw deny 9901/udp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 9901" -Direction Inbound -LocalPort 9901 -Protocol UDP -Action Block  # Windows
04 FAQ
What is port 9901 used for?

Port 9901 is assigned by IANA to enrp (enrp server channel), enrp-sctp (enrp server channel).

Is port 9901 TCP or UDP?

Port 9901 is registered for UDP and SCTP.

Is it safe to open port 9901?

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 9901 is open?

On Linux run "ss -ltnup 'sport = :9901'", on macOS "lsof -nP -i :9901", and on Windows "netstat -ano | findstr :9901" to see the local process. From another machine, "nmap -p 9901 <host>" shows whether it is reachable.

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