What is port 11211 used for?
The Memcached cache server.
Should port 11211 be open?
Don’t expose to the internet. Keep this port on private networks and reach it through a VPN or SSH tunnel. Exposed Memcached powered record-breaking DDoS amplification attacks. Bind to localhost and disable UDP.
See what is listening on port 11211
# Linux
sudo ss -tlnp | grep ':11211 '
# macOS
sudo lsof -nP -i TCP:11211 -sTCP:LISTEN
# Windows (PowerShell)
Get-NetTCPConnection -LocalPort 11211 -State ListenOpen or block port 11211 in a firewall
# Ubuntu / Debian (ufw)
sudo ufw allow 11211
sudo ufw deny 11211
# Windows (PowerShell, as administrator)
New-NetFirewallRule -DisplayName "Port 11211" -Direction Inbound -Protocol TCP -LocalPort 11211 -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 11211 (macOS/Linux) or Test-NetConnection example.com -Port 11211 (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 11211?
The Memcached cache server.
Is it safe to open port 11211?
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 11211 is open?
Enter your domain or public IP in the Port Checker with port 11211. It tries a TCP connection from the internet and reports open, closed or filtered.