The server is a user level program listening to a socket and accepting
connections from clients. It uses portion of the local
workstation's main memory to store the client's pages.
When the client requests a page-in, the server transfers the requested
page(s) over the socket. When the client requests a page-out, the server
reads the incoming pages from the socket, and
stores them in its main memory. 
A backup server responds to page-out requests much like a primary server, but it does not respond to page-in requests unless the client has explicitly declared the primary server as crashed.