ASP.NET Access User Local Network

I am looking into a project where we create a website, usual logins etc but the website will need to access a SQL database local to the user connecting. The server will normally be on a dedicated machine within the network. The users are able to log into that database via software (known to the developers).

I have a few ideas but are unsure of how to implement them such as :

-- Local dedicated server has ports open to WWW where user specifies information on the website for it to connect. Software then modified on local SQL database to talk via those ports and with Web Site

-- User runs an 'applet'? Where they can log into the local SQL database where the applet passes the information to the site from the local SQL.

--Software created for local user that creates file to upload to the website (last resort)

I am hoping to a seemless integration for the user but unsure of the way to go, any advice would be appreciated!

Cheers Tom