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Port 12004 (entextlow)

IANA assigns port 12004 to entextlow: IBM Enterprise Extender SNA COS Low Priority.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
entextlow TCP IBM Enterprise Extender SNA COS Low Priority Eugene Cox -
entextlow UDP IBM Enterprise Extender SNA COS Low Priority Eugene Cox -

Check what is listening on port 12004

Linux: is anything listening on TCP 12004?
sudo ss -tlnp 'sport = :12004'
Linux: UDP 12004
sudo ss -ulnp 'sport = :12004'
Linux / macOS: which process owns the port
sudo lsof -nP -i :12004
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':12004 '
Windows (Command Prompt)
netstat -ano | findstr :12004
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 12004 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 12004
From Windows
Test-NetConnection HOST -Port 12004
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 12004

Block port 12004 in the firewall

ufw
sudo ufw deny 12004/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 12004 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 12004 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 12004' -Direction Inbound -Protocol TCP -LocalPort 12004 -Action Block
ufw
sudo ufw deny 12004/udp
iptables
sudo iptables -A INPUT -p udp --dport 12004 -j DROP
nftables
sudo nft add rule inet filter input udp dport 12004 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 12004' -Direction Inbound -Protocol UDP -LocalPort 12004 -Action Block

Related ports

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