Port 9

discard · DCCP/SCTP/TCP/UDP

RangeSystem/well-known port (0–1023)
ProtocolDCCP/SCTP/TCP/UDP
Servicediscard
ReferenceRFC 9260, RFC 4340
Modified2022-02-07

Frequently asked questions

What is port 9 used for?

Port 9 is registered with the IANA for discard (DCCP/SCTP/TCP/UDP). Description: Discard.

Is port 9 a well-known port?

Yes. Port 9 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 9 is open?

Locally on Linux with ss -tulpn | grep ':9\b', on Windows with netstat -ano | findstr :9. To test a remote host use Test-NetConnection <host> -Port 9 in PowerShell or nc -zv <host> 9 on Linux/macOS.

How do I open port 9 in the firewall?

Ubuntu/Debian (ufw): sudo ufw allow 9/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=9/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 9" -Direction Inbound -Protocol TCP -LocalPort 9 -Action Allow.

IANA registry entries

ProtocolServiceDescription (IANA)
TCPdiscardDiscard
UDPdiscardDiscard
SCTPdiscardDiscard
DCCPdiscardDiscard

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