SQL Server Express를 위한 방화벽 설정

Configure the Windows Firewall to Allow SQL Server Access
; https://docs.microsoft.com/en-us/sql/sql-server/install/configure-the-windows-firewall-to-allow-sql-server-access#BKMK_dynamic_ports

SQL Server named instances in the default configuration The TCP port is a dynamic port determined at the time the Database Engine starts.
See the discussion below in the section Dynamic Ports. UDP port 1434 might be required for the SQL Server Browser Service when you are using named instances.

Configure a Server to Listen on a Specific TCP Port
; https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/configure-a-server-to-listen-on-a-specific-tcp-port

By default, named instances (including SQL Server Express) use dynamic ports. That means that every time that the Database Engine starts, it identifies an available port and uses that port number. If the named instance is the only instance of the Database Engine installed, it will probably use TCP port 1433. If other instances of the Database Engine are installed, it will probably use a different TCP port. Because the port selected might change every time that the Database Engine is started, it is difficult to configure the firewall to enable access to the correct port number. Therefore, if a firewall is used, we recommend reconfiguring the Database Engine to use the same port number every time. This is called a fixed port or a static port. For more information, see Configure a Server to Listen on a Specific TCP Port (SQL Server Configuration Manager).

An alternative to configuring a named instance to listen on a fixed port is to create an exception in the firewall for a SQL Server program such as sqlservr.exe (for the Database Engine). This can be convenient, but the port number will not appear in the Local Port column of the Inbound Rules page when you are using the Windows Firewall with Advanced Security MMC snap-in. This can make it more difficult to audit which ports are open. Another consideration is that a service pack or cumulative update can change the path to the SQL Server executable which will invalidate the firewall rule.