Port 1433: MS SQL
TCP 1433 is the port for Microsoft SQL Server. Never on the internet; brute-force and ransomware crews scan it constantly. Use private networking or a VPN.
| Service | Microsoft SQL Server |
|---|---|
| Protocol | TCP |
| Exposure risk | High: do not expose to the internet |
| Range | Registered (1024–49151) |
What port 1433 does
The default instance of SQL Server listens on TCP 1433; named instances use dynamic ports found through the SQL Browser service on UDP 1434.
Should port 1433 be open?
Never on the internet; brute-force and ransomware crews scan it constantly. Use private networking or a VPN.
Find what's listening on port 1433
- Linux:
sudo ss -tulpn | grep :1433 - macOS:
sudo lsof -nP -i :1433 - Windows:
netstat -ano | findstr :1433, then look up the PID in Task Manager.
Open or block it in a firewall
- ufw:
sudo ufw allow 1433/tcp(ordeny) - firewalld:
sudo firewall-cmd --add-port=1433/tcp --permanent && sudo firewall-cmd --reload - Windows:
New-NetFirewallRule -DisplayName "Port 1433" -Direction Inbound -Protocol TCP -LocalPort 1433 -Action Allow
Port assignment per the IANA Service Name and Transport Protocol Port Number Registry. Test several ports at once with the port scanner, or any port with the open port checker.
Questions about port 1433
What is port 1433 used for?
Microsoft SQL Server. The default instance of SQL Server listens on TCP 1433; named instances use dynamic ports found through the SQL Browser service on UDP 1434.
Is port 1433 TCP or UDP?
TCP. MS SQL uses TCP port 1433.
Is it safe to open port 1433?
High: do not expose to the internet. Never on the internet; brute-force and ransomware crews scan it constantly. Use private networking or a VPN.
How do I check if port 1433 is open?
Use the checker on this page: it connects to your host on TCP 1433 from the internet. Locally, run
nc -vz host 1433 (macOS/Linux) or Test-NetConnection host -Port 1433 (PowerShell). To see what is listening on your own machine, run ss -tulpn | grep :1433 (Linux) or netstat -ano | findstr :1433 (Windows).