Comment 1 for bug 136604

If the PC is on A.C. power the preferred solution would be to set "Put computer to sleep when inactive for" to "Never".

In the 'Power Management Preferences' Help, 'Frequently Asked Questions', 8.4, it says:

"gnome-screensaver is a session daemon that monitors user input, and if the mouse has not been moved, or the keyboard been pressed then it starts a timeout. When the value of this timeout reaches the value set in gnome-screensaver-preferences, then the login is marked as 'session idle'. This is when GNOME Power Manager performs all the session idle actions such as enabling low-power mode and lowering the laptop panel brightness.

As soon as the session is marked at idle, GNOME Power Manager starts it's own 'system' timer. When the timeout set in gnome-power-preferences is reached, and the CPU load is idle, then the idle action is performed, which is usually to turn off the screen, or to suspend or hibernate."

Implementing this suggestion would need Rhythmbox to interact with the power-management features, Many of the scripts for this are distro-specific which would make implementing and maintaining such a function more difficult.

You could create a script that detects when DAAP is active and alters the sleep time-out to "Never" based on if DAAP is listening on a socket, which could be detected using netstat, and have the script run every minute from a cron job. Alternatively, you could use a wrapper script around Rhythmbox that sets the time-out to "Never" before Rhythmbox starts, and restores the original value when it Quits.