Interprocess communication with a Daemon

Use Berkeley sockets. Specifically, you can create a "UNIX domain socket" (otherwise known as a "local domain socket," which will create what looks like a text file. Write to the text file to send text to the daemon, read from it to receive text from the daemon. You can implement this with a few function calls.

If you want something more advanced, you can also use DBus, which offers a more sophisticated interface, but which is more complicated to learn.

use tcp socket if you want to use telnet to communicate with your daemon.