Work performed (or offered) by a server. This may mean simply serving simple requests for data to be sent or stored (as with file servers, gopher or http servers, e-mail servers, finger servers, SQL servers, etc.); or it may be more complex work, such as that of irc servers, print servers, X Windows servers, or process servers.

E.g. "Access to the finger service is restricted to the local subnet, for security reasons".