Any Mac can serve as a content cache, speeding up Apple software updates and certain types of iCloud content.

Content caches can be configured graphically, via System Settings, or via the command:

AssetCacheManagerUtil

On a client, you can see if it can find any content cache by using the command

AssetCacheLocatorUtil

Also, it may be useful to pin the service to a non-random port (e.g. to allow it in your firewall). You can do so with this command:

sudo -u _assetcache defaults write /Library/Preferences/com.apple.AssetCache.plist Port -int 50000

This would pin the service to port 50000.