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Port 481 (ph)

IANA assigns port 481 to ph: Ph service.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
ph TCP Ph service Roland Hedberg -
ph UDP Ph service Roland Hedberg -

Check what is listening on port 481

Linux: is anything listening on TCP 481?
sudo ss -tlnp 'sport = :481'
Linux: UDP 481
sudo ss -ulnp 'sport = :481'
Linux / macOS: which process owns the port
sudo lsof -nP -i :481
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':481 '
Windows (Command Prompt)
netstat -ano | findstr :481
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 481 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 481
From Windows
Test-NetConnection HOST -Port 481
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 481

Block port 481 in the firewall

ufw
sudo ufw deny 481/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 481 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 481 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 481' -Direction Inbound -Protocol TCP -LocalPort 481 -Action Block
ufw
sudo ufw deny 481/udp
iptables
sudo iptables -A INPUT -p udp --dport 481 -j DROP
nftables
sudo nft add rule inet filter input udp dport 481 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 481' -Direction Inbound -Protocol UDP -LocalPort 481 -Action Block

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