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Port 54 (xns-ch)

IANA assigns port 54 to xns-ch: XNS Clearinghouse.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
xns-ch TCP XNS Clearinghouse Susie Armstrong -
xns-ch UDP XNS Clearinghouse Susie Armstrong -

Check what is listening on port 54

Linux: is anything listening on TCP 54?
sudo ss -tlnp 'sport = :54'
Linux: UDP 54
sudo ss -ulnp 'sport = :54'
Linux / macOS: which process owns the port
sudo lsof -nP -i :54
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':54 '
Windows (Command Prompt)
netstat -ano | findstr :54
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 54 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 54
From Windows
Test-NetConnection HOST -Port 54
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 54

Block port 54 in the firewall

ufw
sudo ufw deny 54/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 54 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 54 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 54' -Direction Inbound -Protocol TCP -LocalPort 54 -Action Block
ufw
sudo ufw deny 54/udp
iptables
sudo iptables -A INPUT -p udp --dport 54 -j DROP
nftables
sudo nft add rule inet filter input udp dport 54 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 54' -Direction Inbound -Protocol UDP -LocalPort 54 -Action Block

Related ports

52xns-time53DNS55isi-gl56xns-auth

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.