Make all clients connect to SQL server directly by changing the connection string in all clients to refer to SQL server.

Make all clients PCs contacting the server using stream, TCP or UDP ports ...etc, then the server makes a connection to the database then sends the result to its clients through streams and I/O methods. In other words all clients do not contact the SQL server themselves in a direct manner. Instead they just contact the server PC (this may have the database or not).