epmd

+ EPMD
  - Distributed systems are cool
  - Distributed systems are also complex
  - First step: How to find other machines (and nodes) in the same network
    - Erlang Port Mapper Daemon

+ EPMD in C
  - Ships with Erlang
  - is a TCP server
  - usually 4369
  - binary protocol
  - stateful
  - replaceable

+ ExPMD
  - EPMD written in Elixir
  - Pattern matching on binary strings
  - Still getting used with immutability
  - Using agents to keep data

+ Requests ()
  - Alive -- Sent by new node on start-up
      Registers named node and port (etc) on local EPMD
      Connection remains open until node exits.
  - Port -- Receives a node name
      Returns port registered with given name 
  - Names -- return list of all registered names/ports
  - wireshark

+ Live demo
  - iex --name sophia (alive)
  - Node.ping(:"jv@jv.hackerschool.com")
    - finds EPMD at jv.hackerschool.com
    - asks for node named jv
  - :net_adm.names()