Using UNIX-Domain Sockets
Like TCP/IP sockets, two applications that wish to communicate must rendezvous at an agreed-on name. Instead of using the combination of IP address and port number for rendezvous, UNIX-domain sockets use a path on the local file system, such as /dev/log. They are created automatically when the socket is bound and appear in UNIX directory listings with an "s" at the beginning of the permission string. For example:
% ls -l /dev/log srw-rw-rw- 1 root root 0 Jun 17 16:21 /dev/log
The socket files are not automatically removed after the socket is closed, and must be unlinked manually.
The Perl documentation occasionally refers to these files as "fifo's" because they follow first-in-first-out rules: The first byte of data ...