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Port 12000 (entextxid)

IANA assigns port 12000 to entextxid: IBM Enterprise Extender SNA XID Exchange.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
entextxid TCP IBM Enterprise Extender SNA XID Exchange Eugene Cox -
entextxid UDP IBM Enterprise Extender SNA XID Exchange Eugene Cox -

Check what is listening on port 12000

Linux: is anything listening on TCP 12000?
sudo ss -tlnp 'sport = :12000'
Linux: UDP 12000
sudo ss -ulnp 'sport = :12000'
Linux / macOS: which process owns the port
sudo lsof -nP -i :12000
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':12000 '
Windows (Command Prompt)
netstat -ano | findstr :12000
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 12000 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 12000
From Windows
Test-NetConnection HOST -Port 12000
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 12000

Block port 12000 in the firewall

ufw
sudo ufw deny 12000/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 12000 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 12000 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 12000' -Direction Inbound -Protocol TCP -LocalPort 12000 -Action Block
ufw
sudo ufw deny 12000/udp
iptables
sudo iptables -A INPUT -p udp --dport 12000 -j DROP
nftables
sudo nft add rule inet filter input udp dport 12000 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 12000' -Direction Inbound -Protocol UDP -LocalPort 12000 -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.