Port 27017: MongoDB

What is port 27017 used for?

The default MongoDB port.

Should port 27017 be open?

Don’t expose to the internet. Keep this port on private networks and reach it through a VPN or SSH tunnel. Exposed MongoDB servers have been hit by mass ransom attacks. Bind to private IPs and enable authentication.

See what is listening on port 27017

# Linux
sudo ss -tlnp | grep ':27017 '

# macOS
sudo lsof -nP -i TCP:27017 -sTCP:LISTEN

# Windows (PowerShell)
Get-NetTCPConnection -LocalPort 27017 -State Listen

Open or block port 27017 in a firewall

# Ubuntu / Debian (ufw)
sudo ufw allow 27017/tcp
sudo ufw deny 27017/tcp

# Windows (PowerShell, as administrator)
New-NetFirewallRule -DisplayName "Port 27017" -Direction Inbound -Protocol TCP -LocalPort 27017 -Action Allow

On 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 27017 (macOS/Linux) or Test-NetConnection example.com -Port 27017 (Windows).