Cannot connect to SQL Server Express database from an UWP app

Question

I have a UWP app that needs to connect to a SQL Server Express database. On my dev box, I don't have any issues.

On the client PC, I installed SQL Server Express, created the database, setup the users and logins.

When I run the app, and try to connect to the database, I get an error:

> A network-related or instance-specific error occurred while establishing a connection to SQL Server.
> The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections.
> (provider: TCP Provider, error: 40 - Could not open a connection to SQL Server)

The code I'm using to connect is:

...
using (SqlConnection connection = new SqlConnection(ConnectionStringTextBox.Text.Trim()))
{
    try
    {
        connection.Open();
        MessageBox.Show("Connected successfully!");
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}
...

Using this same code on a desktop app, on the client machine, the connection succeeds.

I have set up the UWP app to use version 1809 of Windows 10.

The client and my dev box are both version 2004.

Package.appxmanifest file has the following capabilities checked:

• Enterprise Authentication
• Internet (Client & Server)
• Internet (Client)
• Private Networks (Client & Server)

Windows Firewall has the correct ports open. In SSMS, I have enabled allowing remote connections, enabled TCP.

I don't know what I'm doing wrong or what is going wrong. This same UWP app works great on my dev box.

Any advice is appreciated.

Answer 1

If client app and SQL Server instance are working on the same machine, it could be loopback issue. You may try following command:

checknetisolation loopbackexempt -a -n=package_family_name

I'm not sure whether this is still true for recent versions of Windows 10, but old versions used to deny connections to localhost.

Answer 2

Please try to test connection with non-UWP tools.

Answer 3

Hello,
if client and SQL Express installed on different machines
I suppose SQL express is not listening on port 1433 (by default only local requests supported)

You have to run SQL server configuration manager and Enable TCP/IP in SQL server network configuration
and restart SQL express (or entire PC/server where you have installed it)

to check port connectivity, open SMSS on another PC and connect to server:

tcp:Servername, 1433