$ sudo launchctl list might help you to get a list of running daemons. When the first column (PID) is actually not a minus-sign, than it is running. Otherwise the launchd job is loaded and waiting in the background to be started on the corresponding event.

One of the output lines could be:

33  -   com.apple.notifyd

Next you need to find where its plist file is stored.

$ locate com.apple.notifyd

Helps here, with output:

/System/Library/LaunchDaemons/com.apple.notifyd.plist
...

Finally the command to restart is:

$ sudo launchctl unload /System/Library/LaunchDaemons/com.apple.notifyd.plist;sudo launchctl load /System/Library/LaunchDaemons/com.apple.notifyd.plist

As the Messages beta application is no longer available for download from Apple, I can't give the exact commands. Below is a general answer.

$ sudo launchctl list might help you to get a list of running daemons. When the first column (PID) is actually not a minus-sign, than it is running. Otherwise the launchd job is loaded and waiting in the background to be started on the corresponding event.

One of the output lines could be:

33  -   com.apple.notifyd

Next you need to find where its plist file is stored.

$ locate com.apple.notifyd

Helps here, with output:

/System/Library/LaunchDaemons/com.apple.notifyd.plist
...

Finally the command to restart is:

$ sudo launchctl unload /System/Library/LaunchDaemons/com.apple.notifyd.plist;sudo launchctl load /System/Library/LaunchDaemons/com.apple.notifyd.plist