SharePoint Server Configuration Database SQL Not Using Default Port
After you install SharePoint 2007 or 2010 on a new server and run SharePoint Products Configuration Wizard to create new farm configuration database or connect to existing configuration database you need to provide server name of a server running SQL server. When that SQL server is on a remote (remote to SharePoint) box and runs on a standard TCP port (1433) there is no problem (assuming firewall rules allow connecting to that server on port 1433). However if the SQL server is configured to accept connection on a non-default (custom) TCP port (ex: TCP port 28321) then Configuration Wizard will fail even if you specify port number as part of a server name (ex: sqlserver1.domain.local,28321).
Instead what you need to do is go to Start select Run and type cliconfg.exe and press Enter. This will launch the SQL Server Client Network Utility. You can use this utility to create an "Alias" (in the Alias tab) for the target SQL server and specify the non-standard port. Click on the Alias tab, then click Add. In the Server alias box on the top of the screen type the FQDN server name (ex: sqlserver1.domain.local) then select TCP/IP from the Network libraries section and uncheck the Dynamically determine port checkbox. In the Port number box type the custom SQL TCP port (ex: 23831) and hit OK, then Apply the changes and re-run the SharePoint Configuration Wizard.
Once you do so you will be able to type just the FQDN server name in the Database server box and proceed with the configuration.