What is port 389 used for?
Lightweight Directory Access Protocol: directory lookups, including Active Directory.
Should port 389 be open?
Don’t expose to the internet. Keep this port on private networks and reach it through a VPN or SSH tunnel. Directory servers belong on internal networks. Use LDAPS (636) or StartTLS for encryption.
See what is listening on port 389
# Linux
sudo ss -tlnp | grep ':389 '
# macOS
sudo lsof -nP -i TCP:389 -sTCP:LISTEN
# Windows (PowerShell)
Get-NetTCPConnection -LocalPort 389 -State ListenOpen or block port 389 in a firewall
# Ubuntu / Debian (ufw)
sudo ufw allow 389
sudo ufw deny 389
# Windows (PowerShell, as administrator)
New-NetFirewallRule -DisplayName "Port 389" -Direction Inbound -Protocol TCP -LocalPort 389 -Action AllowOn cloud servers, also open the port in the provider’s security group or network firewall. At home, a service behind a router needs a port-forwarding rule to the device’s local IP.
Test it from outside
A port can be open on the server but blocked upstream. The Port Checker connects from the internet, so it shows what the world sees. From your own machine, use nc -vz example.com 389 (macOS/Linux) or Test-NetConnection example.com -Port 389 (Windows).
Port CheckerTest whether a server accepts connections on specific ports — web (80/443), mail (25/587/993), SSH, databases or remote desktop — and see which are open, closed or filtered by a firewall.
Open the tool Frequently asked questions
What is port 389?
Lightweight Directory Access Protocol: directory lookups, including Active Directory.
Is it safe to open port 389?
Don’t expose to the internet. Keep this port on private networks and reach it through a VPN or SSH tunnel.
How do I check if port 389 is open?
Enter your domain or public IP in the Port Checker with port 389. It tries a TCP connection from the internet and reports open, closed or filtered.