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Port 436 (dna-cml)

IANA assigns port 436 to dna-cml: DNA-CML.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
dna-cml TCP DNA-CML Dan Flowers -
dna-cml UDP DNA-CML Dan Flowers -

Check what is listening on port 436

Linux: is anything listening on TCP 436?
sudo ss -tlnp 'sport = :436'
Linux: UDP 436
sudo ss -ulnp 'sport = :436'
Linux / macOS: which process owns the port
sudo lsof -nP -i :436
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':436 '
Windows (Command Prompt)
netstat -ano | findstr :436
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 436 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 436
From Windows
Test-NetConnection HOST -Port 436
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 436

Block port 436 in the firewall

ufw
sudo ufw deny 436/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 436 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 436 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 436' -Direction Inbound -Protocol TCP -LocalPort 436 -Action Block
ufw
sudo ufw deny 436/udp
iptables
sudo iptables -A INPUT -p udp --dport 436 -j DROP
nftables
sudo nft add rule inet filter input udp dport 436 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 436' -Direction Inbound -Protocol UDP -LocalPort 436 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.