HTTPfy

Port 689 (nmap)

IANA assigns port 689 to nmap: NMAP.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
nmap TCP NMAP Peter Dennis Bartok -
nmap UDP NMAP Peter Dennis Bartok -

Check what is listening on port 689

Linux: is anything listening on TCP 689?
sudo ss -tlnp 'sport = :689'
Linux: UDP 689
sudo ss -ulnp 'sport = :689'
Linux / macOS: which process owns the port
sudo lsof -nP -i :689
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':689 '
Windows (Command Prompt)
netstat -ano | findstr :689
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 689 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 689
From Windows
Test-NetConnection HOST -Port 689
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 689

Block port 689 in the firewall

ufw
sudo ufw deny 689/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 689 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 689 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 689' -Direction Inbound -Protocol TCP -LocalPort 689 -Action Block
ufw
sudo ufw deny 689/udp
iptables
sudo iptables -A INPUT -p udp --dport 689 -j DROP
nftables
sudo nft add rule inet filter input udp dport 689 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 689' -Direction Inbound -Protocol UDP -LocalPort 689 -Action Block

Related ports

687asipregistry688realm-rusd690vatp691msexch-routing

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