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SQL Server: The TCP/IP connection to the host localhost x has failed

This error indicates that Runtime has attempted to connect to a MSSQL database, and was unable to do so due to a networking error.

Causes & Resolutions

This issue can be caused by a variety of things, such as:

  • TCP/IP connections are not enabled on the SQL Server. Enable this here: Start → Microsoft SQL Server → Configuration Tools → SQL Server Configuration Manager → SQL Server Network Configuration → Protocols for SQLExpress

  • No TCP loopback address defined.

  • Sometimes, TCP Dynamic ports can cause issues. To resolve this, remove All TCP Dynamic Ports and add a set value (by default, this is 1433) to all TCP Ports and restart your SQL Server Services > SQL Server

  • If none of the above have helped, it might be that the firewall is blocking traffic between Runtime and the SQL Server. To troubleshoot this, refer to your local system administrator.

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