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Port 2004 (emce)

IANA assigns port 2004 to emce: CCWS mm conf.

Registered (user) port, 1024-49151 UDP

Port 2004 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

IANA assignment

Service nameProtoDescriptionAssigneeReference
emce UDP CCWS mm conf - -

Check what is listening on port 2004

Linux: UDP 2004
sudo ss -ulnp 'sport = :2004'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2004
Windows (Command Prompt)
netstat -ano | findstr :2004
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 2004

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2004

Block port 2004 in the firewall

ufw
sudo ufw deny 2004/udp
iptables
sudo iptables -A INPUT -p udp --dport 2004 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2004 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2004' -Direction Inbound -Protocol UDP -LocalPort 2004 -Action Block

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