Port 9909 (domaintime)

IANA assigns port 9909 to domaintime.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference

domaintime TCP domaintime Jeffry Dwight -

domaintime UDP domaintime Jeffry Dwight -

Linux: is anything listening on TCP 9909?

sudo ss -tlnp 'sport = :9909'

Linux: UDP 9909

sudo ss -ulnp 'sport = :9909'

Linux / macOS: which process owns the port

sudo lsof -nP -i :9909

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':9909 '

Windows (Command Prompt)

netstat -ano | findstr :9909

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9909 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 9909

From Windows

Test-NetConnection HOST -Port 9909

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 9909

ufw

sudo ufw deny 9909/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 9909 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 9909 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 9909' -Direction Inbound -Protocol TCP -LocalPort 9909 -Action Block

ufw

sudo ufw deny 9909/udp

iptables

sudo iptables -A INPUT -p udp --dport 9909 -j DROP

nftables

sudo nft add rule inet filter input udp dport 9909 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 9909' -Direction Inbound -Protocol UDP -LocalPort 9909 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.