I’ve just discovered a handy command for macOS that will show you Apple Caching Service servers that are available to your Mac. It lives in:

/usr/bin/AssetCacheLocatorUtil

From the man page:

AssetCacheLocatorUtil reports information related to macOS Server caching servers running on the computer or on the local network.

Some of the information that AssetCacheLocatorUtil reports depends on the current network configuration, and on the user running it.  It might produce different results for different users, on different client devices, or on different networks.  Applications that use caching servers might choose ones other than the ones AssetCacheLocatorUtil reports due to factors beyond its knowledge, such as iCloud affinity.

Charles Edge over at krypted, has some more info on the service – including a handy snippet that parses the output and shows you the IP addresses of the Caching Service servers that your Mac is able to find

/usr/bin/AssetCacheLocatorUtil 2>&1 | grep guid | awk '{print$4}' | sed 's/^\(.*\):.*$/\1/' | uniq

Remember that in High Sierra, the Caching Service is now built into the OS, you don’t need macOS Server.app installed to use this service.