Using wildcards in socket addresses (Internet domain only)
A server can use the wildcard symbol ``*'' to
underspecify its location in order to service incoming requests
from multiple network interfaces.
A service such as ftp can be installed only once on a
host which is connected to multiple network interfaces. The
ftp program can listen on all the network interfaces:
<<*.21> <*.*>>This tuple signifies that the local ftp on port 21 is listening on multiple interface addresses for whatever client processes that wish to connect.
To name a socket that listens on all network interfaces, the Internet address INADDR_ANY must be bound. If a listening port is not specified, the system assigns one. For more information on wildcarding, see ``Internet address binding''.