A super basic WS server

bsocial.ex

defmodule Bsocial do
  use Application
  def start(_type, _args) do
    import Supervisor.Spec

    children = [
      supervisor(Task.Supervisor, [[name: Bsocial.ConnectionsSupervisor]]),
      worker(Task, [Bsocial.Server, :start, [4000]])
    ]

    opts = [strategy: :one_for_one, name: Bsocial.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

server.ex

defmodule Bsocial.Server do
  def start(port) do
    server = Socket.Web.listen! port

    # For now, we keep it to one chat room for PoC simplicity
    name = Bsocial.Chat
    :pg2.create(name: name)
    loop_acceptor(server, name)
  end

  defp loop_acceptor(server, chat_name) do
    client = server |> Socket.Web.accept!
    client |> Socket.Web.accept!

    # Start our message sending process
    {:ok, messaging_pid} = Task.Supervisor.start_child(Bsocial.ConnectionsSupervisor, fn -> handle_messages(client, chat_name) end)
    :pg2.join(chat_name, messaging_pid)
    {:ok, _} = Task.Supervisor.start_child(Bsocial.ConnectionsSupervisor, fn -> serve(client, messaging_pid) end)

    loop_acceptor(server, chat_name)
  end

  defp serve(client, messagingProcess) do
    message = client |> Socket.Web.recv!

    send(messagingProcess, {:external, message})

    serve(client, messagingProcess)
  end

  defp handle_messages(client, chat_name) do
    receive do
      {:internal, message} ->
        # It's internal so it should be sent to client
        client |> Socket.Web.send!(message)
      {:external, message} ->
        # A new message arrived from a web client, send to other connections
        # Fetch the PIDs of other connections in the channel
        members = :pg2.get_members(chat_name)
        # broadcast it to the other connections
        for process <- members, process != self() do
          send(process, message)
        end
      _ ->
        # Something's probably wrong, throw an error or handle it ¯\_(ツ)_/¯
        throw {:error, "Unrecognized sender"}
    end
  end
end