Thank you for replying!
However, I've setup my own cataclysm client and server (https://github.com/The-Cataclysm-Preservation-Project/TrinityCore) and it still works (it is still downloading in the background), so I think this is different from what you are describing.
After a bit of research, I've discovered that there is a file: WoW.mfil that describes the server that they are using:
So they are using limelight (after googling it turns out to be a cdn)
and they have these addresses:
when you add manifest_partial to the first address you get this:
If you click on that link you'll actually find a document containing the paths, sizes, locales of the all MPQ files needed by the client.
it seems that this manifest_partial tells the client where to download these files.
We can actually append the path of the MPQ files to the address and get the file like so:
Downloading world.MPQ for example:
So how are they setting up their server? Is it simply serving this document on the manfiest_partial endpoint and hosting the MPQ files?
This seems too good to be true.
Again, If anyone got any ideas please share!