HTTPfy

Port 12003 (entextmed)

IANA assigns port 12003 to entextmed: IBM Enterprise Extender SNA COS Medium Priority.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
entextmed TCP IBM Enterprise Extender SNA COS Medium Priority Eugene Cox -
entextmed UDP IBM Enterprise Extender SNA COS Medium Priority Eugene Cox -

Check what is listening on port 12003

Linux: is anything listening on TCP 12003?
sudo ss -tlnp 'sport = :12003'
Linux: UDP 12003
sudo ss -ulnp 'sport = :12003'
Linux / macOS: which process owns the port
sudo lsof -nP -i :12003
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':12003 '
Windows (Command Prompt)
netstat -ano | findstr :12003
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 12003 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 12003
From Windows
Test-NetConnection HOST -Port 12003
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 12003

Block port 12003 in the firewall

ufw
sudo ufw deny 12003/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 12003 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 12003 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 12003' -Direction Inbound -Protocol TCP -LocalPort 12003 -Action Block
ufw
sudo ufw deny 12003/udp
iptables
sudo iptables -A INPUT -p udp --dport 12003 -j DROP
nftables
sudo nft add rule inet filter input udp dport 12003 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 12003' -Direction Inbound -Protocol UDP -LocalPort 12003 -Action Block

Related ports

12001entextnetwk12002entexthigh12004entextlow12005dbisamserver1

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