[Plasma] How did the Plasma's Domain Unix Socket provide the mmap?

Hi, I'm considering how the Plasma use the Unix socket to delivery a memory mapping between different processes? I suppose it is the plasma's server's Unix socket just send the file descriptor (namely the Unix' fd) of a certain  temp file on disk it opened to all the clients, and then the client

[Plasma] Will Plasma provide a cluster version?

Hi, I'm wondering if the Plasma can works well between  client process on different cluster nodes for sharing the data ?  Or if it will be a new feature for  later Apache Arrow's new release?