Was running into the following error while installing JIRA: “Network error IOException: Connection refused”. It seems that the SQL Server Express installer doesn’t enable the TCP/IP protocol by default.
You can enable the option within the SQL Server Configuration Manager and restart the SQL service however, I prefer using PowerShell and SMO (Slightly altered version of the following blog post).
JIRA SQL Server configure TCP/IP
Enables the TCP/IP protocol for all available SQL Server Instances.