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B.13. Networking and IPC
If
there's a way that
programs on your machine can talk with others, Perl can probably do
it. This section shows some common ways.
B.13.1. System V IPC
The standard functions for System V IPC (interprocess
communication) are all supported by Perl, so you can use message
queues, semaphores, and shared memory. Of course, an array in Perl
isn't stored in a chunk of memory in the same way[409] that an array is stored in C, so shared memory
can't share Perl data as-is. But there are modules that will
translate data, so that you can pretend that your Perl data is in
shared memory. See the
perlfunc
manpage and the
perlipc module.
[409]In fact, it would generally be a lie to say that a Perl array
is stored in "a chunk of memory" at all, as it's
almost certainly spread among many separate chunks.
B.13.2. Sockets
Perl has full support for TCP/IP sockets, which means that you
could write a web server in Perl, or a web browser, Usenet news
server or client, finger daemon or client, FTP daemon or client, SMTP
or POP or SOAP server or client, or either end of pretty much any
other kind of protocol in use on the
Internet. Of course, there's no need
to get into the low-level details yourself; there are modules
available for all of the common protocols. For example, you can make
a web server or client with the
LWP module and one or two lines of
additional code.[410] The LWP module (actually,
a tightly integrated set of modules, which together implement nearly
everything that happens on the Web) is also a great example of
high-quality Perl code, if you'd like to copy from the best.
For other protocols, search for a module with the protocol's
name.
[410]Although LWP
makes it easy to make a simple "web browser" that pulls
down a page or image, actually rendering that to the user is another
problem. You can drive an X11 display with Tk or Gtk widgets though,
or use curses to draw on a character terminal. It's all a
matter of downloading and installing the right modules from
CPAN.
