8.1. UNIX-Domain Sockets
This is a socket which is not reachable from the Internet directly, but which must come from a request on the server. The link program vlink is the provided facility for such communication with Interchange. This is the most secure way to run a catalog, for there is no way for systems on the Internet to interact with Interchange except through its link program.
The most important issue with UNIX-domain sockets on Interchange is the permissions with which the CGI program and the Interchange server run. To improve security, Interchange normally runs with the socket file having 0600 permissions (rw-------), which mandates that the CGI program and the server run as the same user ID. This means that the vlink program must be SUID to the same user ID as the server executes under. (Or that CGIWRAP is used on a single catalog system).
With Interchange's multiple catalog capability, the permissions situation gets a bit tricky. Interchange comes with a program, makecat, which configures catalogs for a multiple catalog system. It should properly set up ownership and permissions for multiple users if run as the superuser.