Attaching to Another Node

Introduction

In this notebook we connect to another BEAM node, spawn a process on it, and communicate with this process.

Before we begin, we need to start a BEAM node somewhere else. This can be done by starting an iex session:

iex --name test@127.0.0.1 --cookie mycookie

Configuration

node = :"test@127.0.0.1"
cookie = :mycookie

Connect

Node.set_cookie(node, cookie)
Node.connect(node)

List connected nodes (some are hidden by default):

Node.list(:connected)

Start Remote Process

The following code spawns a new process on node. This process blocks until it has received a message patching the {:ping, org_pid} pattern. When that happens, a response is sent back that contains the remote node identity and the remote process pid.

pid = Node.spawn_link(node, fn ->
  receive do
    {:ping, org_pid} -> send(org_pid, {:pong, Node.self(), self()})
  end
  end)

Note: The first component of the pid looks different from the usual 0. This is a numerical node id. A non-zero node id means that the process is hosted remotely.

Communicate

Send message to remote pid that includes our own pid:

send(pid, {:ping, self()})

Block until the response has arrived:

receive do
  message -> message
end