You probably want the daemon to listen on some port with IO::Socket::UNIX or IO::Socket::INET. If you want to get modern, have POE do the heavy lifting. Its cookbook has examples which would probably take little work to adapt to your requirements.

You can't really have a daemon watch for keyboard activity. A daemon has no controlling terminal, so whose keystrokes should it watch? The point of a daemon is that whoever wants to use it should connect in a known way. It's up to the client to produce the socket message on an event. That way the daemon doesn't need to know anything about the client.