Port 433

nnsp · TCP/UDP

RangeSystem/well-known port (0–1023)
ProtocolTCP/UDP
Servicennsp
ReferenceRFC 3977
Modified2018-07-06

Frequently asked questions

What is port 433 used for?

Port 433 is registered with the IANA for nnsp (TCP/UDP). Description: NNTP for transit servers (NNSP).

Is port 433 a well-known port?

Yes. Port 433 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 433 is open?

Locally on Linux with ss -tulpn | grep ':433\b', on Windows with netstat -ano | findstr :433. To test a remote host use Test-NetConnection <host> -Port 433 in PowerShell or nc -zv <host> 433 on Linux/macOS.

How do I open port 433 in the firewall?

Ubuntu/Debian (ufw): sudo ufw allow 433/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=433/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 433" -Direction Inbound -Protocol TCP -LocalPort 433 -Action Allow.

IANA registry entries

ProtocolServiceDescription (IANA)
TCPnnspNNTP for transit servers (NNSP)
UDPnnspNNTP for transit servers (NNSP)

Nearby entries