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Port 404 (nced)

IANA assigns port 404 to nced.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
nced TCP nced - -
nced UDP nced - -

Check what is listening on port 404

Linux: is anything listening on TCP 404?
sudo ss -tlnp 'sport = :404'
Linux: UDP 404
sudo ss -ulnp 'sport = :404'
Linux / macOS: which process owns the port
sudo lsof -nP -i :404
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':404 '
Windows (Command Prompt)
netstat -ano | findstr :404
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 404 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 404
From Windows
Test-NetConnection HOST -Port 404
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 404

Block port 404 in the firewall

ufw
sudo ufw deny 404/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 404 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 404 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 404' -Direction Inbound -Protocol TCP -LocalPort 404 -Action Block
ufw
sudo ufw deny 404/udp
iptables
sudo iptables -A INPUT -p udp --dport 404 -j DROP
nftables
sudo nft add rule inet filter input udp dport 404 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 404' -Direction Inbound -Protocol UDP -LocalPort 404 -Action Block

Related ports

402genie403decap405ncld406imsp

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