InformationIf enabled, the default SQL Server instance will be assigned a default port of TCP:1433 for TCP/IP communication. Administrators can also configure named instances to use TCP:1433 for communication. TCP:1433 is a widely known SQL Server port and this port assignment should be changed.
Using a non-default port helps protect the database from attacks directed to the default port.
SolutionIn SQL Server Configuration Manager, in the console pane, expand SQL Server Network Configuration, expand Protocols for <InstanceName>, and then double-click the TCP/IP or VIA protocol
In the TCP/IP Properties dialog box, on the IP Addresses tab, several IP addresses appear in the format IP1, IP2, up to IPAll. One of these is for the IP address of the loopback adapter, 127.0.0.1. Additional IP addresses appear for each IP Address on the computer
Change the TCP Port field from 1433 to another non-standard port or leave the TCP Port field empty and set the TCP Dynamic Ports value to 0 to enable dynamic port assignment and then click OK.
In the console pane, click SQL Server Services.
In the details pane, right-click SQL Server (<InstanceName>) and then click Restart, to stop and restart SQL Server.
Changing the default port will force the DAC (Dedicated Administrator Connection) to listen on a random port. Also, it might make benign applications, such as application firewalls, require special configuration. In general, you should set a static port for consistent usage by applications, including firewalls, instead of using dynamic ports which will be chosen randomly at each SQL Server start up.
By default, default SQL Server instances listen on to TCP/IP traffic on TCP port 1433 and named instances use dynamic ports.