Port 1433: Microsoft SQL Server

What is port 1433 used for?

The default SQL Server database port.

Should port 1433 be open?

Don’t expose to the internet. Keep this port on private networks and reach it through a VPN or SSH tunnel. Databases exposed to the internet are brute-forced around the clock. Allow only application servers, or connect through a VPN or SSH tunnel.

See what is listening on port 1433

# Linux
sudo ss -tlnp | grep ':1433 '

# macOS
sudo lsof -nP -i TCP:1433 -sTCP:LISTEN

# Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1433 -State Listen

Open or block port 1433 in a firewall

# Ubuntu / Debian (ufw)
sudo ufw allow 1433/tcp
sudo ufw deny 1433/tcp

# Windows (PowerShell, as administrator)
New-NetFirewallRule -DisplayName "Port 1433" -Direction Inbound -Protocol TCP -LocalPort 1433 -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 1433 (macOS/Linux) or Test-NetConnection example.com -Port 1433 (Windows).