Enable TCP/IP Port for MSSQL Server 2005/2008/2012

Behavior:
When installing DocuWare on a Microsoft SQL Server, it may happen that one of the following messages is displayed:

"The TCP/IP port of the MSSQL 20xx is not enabled"
OR
"The SQL Server you are trying to access accepts only local connections!"

In the DWSetup.log, the following message can be found:
"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: 0 - No connection could be made because the target machine actively refused it.)"

Solution:
Open the "SQL Server Configuration Manager" via the start menu and go to "SQL Server Network Configuration" -> "Protocol for MSSQL Server". Most likely the option "TCP/IP" is disabled:


To activate the TCP/IP Port, adapt the following setting:


Additionally there are some settings in the tab "IP Adresses" that should be adapted for IPv4 addresses too. Make sure, that a static or a dynamic port is entered