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Port 499 (iso-ill)

IANA assigns port 499 to iso-ill: ISO ILL Protocol.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
iso-ill TCP ISO ILL Protocol Mark H Needleman -
iso-ill UDP ISO ILL Protocol Mark H Needleman -

Check what is listening on port 499

Linux: is anything listening on TCP 499?
sudo ss -tlnp 'sport = :499'
Linux: UDP 499
sudo ss -ulnp 'sport = :499'
Linux / macOS: which process owns the port
sudo lsof -nP -i :499
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':499 '
Windows (Command Prompt)
netstat -ano | findstr :499
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 499 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 499
From Windows
Test-NetConnection HOST -Port 499
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 499

Block port 499 in the firewall

ufw
sudo ufw deny 499/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 499 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 499 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 499' -Direction Inbound -Protocol TCP -LocalPort 499 -Action Block
ufw
sudo ufw deny 499/udp
iptables
sudo iptables -A INPUT -p udp --dport 499 -j DROP
nftables
sudo nft add rule inet filter input udp dport 499 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 499' -Direction Inbound -Protocol UDP -LocalPort 499 -Action Block

Related ports

497retrospect498siam500IKE (IPsec)501stmf

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