Open Connection from Mono Image to SQL Server running on the host

Hi,
I try to open a SQL connection from my .NET 4.6.1 application to the SQL Server that is running on the host (Windows 10).
In the SQL Server Configuration Manager I enabled TCP/IP and made sure, that the SQL Server ist listening on all IP addresses.
In my Bitdefender (AntiVirus) I enabled Inbound and Outbound connections to the SQL Server default port 1433.

I tried different ConnectionStrings.

With the connection string

server=192.168.204.49\SQLEXPRESS2017,1433;user id=myuserid;password=mypw;initial catalog=mydatabase;MultipleActiveResultSets=True

I receive the error message:

Snix_PreLogin (provider: SNI_PN7, error: 0 - Cannot find the specified file)
Snix_PreLogin (provider: SNI_PN7, error: 0 - Cannot find the specified file)
Snix_PreLogin (provider: SNI_PN7, error: 0 - Cannot find the specified file)
Cannot find the specified file

at System.Data.ProviderBase.DbConnectionPool.TryGetConnection (System.Data.Common.DbConnection owningObject, System.UInt32 waitForMultipleObjectsTimeout, System.Boolean allowCreate, System.Boolean onlyOneCheckConnection, System.Data.Common.DbConnectionOptions userOptions, System.Data.ProviderBase.DbConnectionInternal& connection) [0x00085] in :0

  • at System.Data.ProviderBase.DbConnectionPool.TryGetConnection*

After I changed the connection string to

server=host.docker.internal\SQLEXPRESS2017,1433;user id=myuserid;password=mypw;initial catalog=mydatabase;MultipleActiveResultSets=True

I get the following error:

System.Data.SqlClient.SqlException (0x80131904): Snix_PreLogin (provider: SNI_PN7, error: 0 - Cannot find the specified file)
Snix_PreLogin (provider: SNI_PN7, error: 0 - Cannot find the specified file) —> System.ComponentModel.Win32Exception (0x80004005): Cannot find the specified file

I start the container with the following command:

docker run -i -t -p 1433:1433 [tagged name]

What can I do to enable the connection from the Docker Containers .NET 4.6.1 application to my local SQL Server?
Regards,
Christian