I don't remember where I learned about restricting sockets to specific addresses, and I can't find any really descriptive information on it. Very frustrating... :(

Here is a relevant snippet from perlipc:

       And here's a corresponding server to go along with it.
       We'll leave the address as INADDR_ANY so that the kernel
       can choose the appropriate interface on multihomed hosts.
       If you want sit on a particular interface (like the
       external side of a gateway or firewall machine), you
       should fill this in with your real address instead.
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And here's something from Socket:

       INADDR_ANY
            Note: does not return a number, but a packed string.
 
            Returns the 4-byte wildcard ip address which
            specifies any of the hosts ip addresses. (A
            particular machine can have more than one ip address,
            each address corresponding to a particular network
            interface. This wildcard address allows you to bind
            to all of them simultaneously.)  Normally equivalent
            to inet_aton('0.0.0.0').
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Let's say you have a machine that has two IP addresses: mymachine.example.com and foo.bar.baz.com. A server program which binds to the address mymachine.example.com will only accept connections made to mymachine.example.com. A program which binds to foo.bar.baz.com will only accept connections to foo.bar.baz.com, and a program that binds to localhost will only accept connections to localhost (which must, of course, also be from localhost).

On the other hand, a server program which binds to INADDR_ANY will accept connections made to any address that happens to resolve to the machine in question, including mymachine.example.com, foo.bar.baz.com, and localhost. That's usually what you want.