Port 1433 (MS SQL Server)
Port 1433 is the default TCP port of the Microsoft SQL Server database engine. Named instances often use dynamic ports instead, announced by the SQL Server Browser service on UDP 1434.
- Service
- MS SQL Server
- Protocol
- TCP
- IANA registry
- Officially assigned: ms-sql-s (Microsoft-SQL-Server), TCP/UDP
Check if a port is open on your IP
We only check the address you are visiting from, one TCP port at a time. You cannot enter someone else’s address: this is not a port scanner.
Is it safe to open port 1433?
A database should not be reachable from the whole internet. Allow 1433 only from your application servers or over a VPN, and disable the sa login or give it a long random password: exposed SQL Servers are a common target of password guessing.
Sources
“Port 1433 is already in use”: how to fix it
The error means another program is already listening on port 1433. Find its process ID (PID), then stop that program or start yours on a different port.
Windows (Command Prompt or PowerShell as administrator)
netstat -ano | findstr :1433taskkill /PID <PID> /FmacOS
lsof -nP -iTCP:1433 -sTCP:LISTENkill <PID>Linux
sudo ss -ltnp | grep :1433sudo lsof -i :1433sudo kill <PID>Replace <PID> with the number from the last column (Windows) or the PID column (macOS, Linux).
Why a port can look closed when your server is running
Most home networks sit behind a router doing NAT: the router owns the public address, and your computer has a private one such as 192.168.1.10. A connection from the internet reaches the router and stops there unless you add a port forwarding rule to your computer.
Many mobile and some home providers go further and use carrier-grade NAT (CGNAT): several customers share one public address, and your router itself gets an address from 100.64.0.0/10. Then no rule on your side can open a port; ask the provider for a public IP or use a tunnel or VPN service.
Even with forwarding in place, the firewall on the computer (Windows Defender Firewall, ufw, firewalld) must allow the port, and the program must listen on all interfaces (0.0.0.0), not only on 127.0.0.1.
UDP cannot be checked this way: a UDP service usually stays silent to packets it does not understand, so “no answer” means nothing. This check uses TCP only.
Frequently asked questions
What is port 1433 used for?
Port 1433 is the default TCP port of the Microsoft SQL Server database engine. Named instances often use dynamic ports instead, announced by the SQL Server Browser service on UDP 1434.
Is port 1433 TCP or UDP?
Port 1433 uses TCP. IANA reserves the number for both TCP and UDP, but in practice only TCP is used.
Is it safe to open port 1433?
A database should not be reachable from the whole internet. Allow 1433 only from your application servers or over a VPN, and disable the sa login or give it a long random password: exposed SQL Servers are a common target of password guessing.
How do I free port 1433 if it is already in use?
Find the process: on Windows run netstat -ano | findstr :1433 and stop it with taskkill /PID <pid> /F; on macOS or Linux run lsof -i :1433 and stop it with kill <pid>.