Port 1433

Port 1433 is primarily used by Microsoft SQL Server to listen for incoming connection requests utilizing the Tabular Data Stream (TDS) protocol over TCP. Clients, including SQL Server Management Studio and custom applications, use it to authenticate, execute queries, and perform database management. Because it enables database transactions and command execution, this port is essential for both day-to-day operations and automated system tasks.

SQL Server supports multiple network libraries and can be configured to use other ports or named pipes, but port 1433 remains the default for most TCP/IP connections. This port is associated with the main database engine and not with auxiliary services like SQL Server Agent or Reporting Services, which may use different ports. In environments with multiple instances, the SQL Server Browser service helps redirect clients to the correct dynamic port, though the default instance usually remains on 1433.

From a deployment perspective, exposing port 1433 to untrusted networks introduces risk. Many organizations choose to change the default port or restrict access via firewall rules, VPNs, or network segmentation, especially in cloud-hosted or internet-facing scenarios, to reduce exposure and manage connections more securely.