getpeereid

        # BasicSocket.getpeereid

(from ruby core)
---
    basicsocket.getpeereid => [euid, egid]

---

Returns the user and group on the peer of the UNIX socket. The result is
a two element array which contains the effective uid and the effective
gid.

    Socket.unix_server_loop("/tmp/sock") {|s|
      begin
        euid, egid = s.getpeereid

        # Check the connected client is myself or not.
        next if euid != Process.uid

        # do something about my resource.

      ensure
        s.close
      end
    }