Port 991

nas · TCP/UDP

RangeSystem/well-known port (0–1023)
ProtocolTCP/UDP
Servicenas
ReferenceRFC 4707
Modified2017-02-10

Frequently asked questions

What is port 991 used for?

Port 991 is registered with the IANA for nas (TCP/UDP). Description: Netnews Administration System.

Is port 991 a well-known port?

Yes. Port 991 is in the range 0–1023 (system or well-known ports). On Linux and macOS only privileged processes may bind to these ports.

How do I check whether port 991 is open?

Locally on Linux with ss -tulpn | grep ':991\b', on Windows with netstat -ano | findstr :991. To test a remote host use Test-NetConnection <host> -Port 991 in PowerShell or nc -zv <host> 991 on Linux/macOS.

How do I open port 991 in the firewall?

Ubuntu/Debian (ufw): sudo ufw allow 991/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=991/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 991" -Direction Inbound -Protocol TCP -LocalPort 991 -Action Allow.

IANA registry entries

ProtocolServiceDescription (IANA)
TCPnasNetnews Administration System
UDPnasNetnews Administration System

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