Unless both machines are on the same network, this either can't easily be done, or you need crazy security settings. If the machines are on the same network, you could save it at \\Servername\Share
Otherwise, you need a mechanism at the other server to accept the file in a different way. Options that come to mind are FTP or a web service.
Can you please post questions not directly related to my book(such as this one) in a more general ASP.NET category: http://p2p.wrox.com/asp-net-4-539/