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Functional Web Development with Elixir, OTP and Phoenix

Communication Between Players

Explore how to enable real-time communication between players using Phoenix Channels in Elixir. Learn to use push and broadcast functions to send messages and events to individual users or all connected clients. Understand how to set up event listeners on the client side and manage persistent connections to create scalable interactive web applications.

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Communication between the players

Now, let’s look at how push/3 works inside the GameChannel. Instead of a reply tuple, this will send a new event down the Channel, but only to the original caller. Since we don’t rely on a reply tuple to communicate back to the client, we replace it with {:noreply, socket}.

The path of message passing will look the same as the reply shown in the following figure.

Let’s go to the Channel and change the handle_in/3 clause to use push/3. We could leave the :reply tuple there and get two responses. However, since push/3 will already send a reply, it makes more sense to swap in {:noreply, socket} instead:

Let’s compile the GameChannel so we can see handle_in/3 in action:

def handle_in("hello", payload, socket) do
  push socket, "said_hello", payload 
  {:noreply, socket}
end

New IEx session

Now, let’s head over to Player 1’s console and give it a try:

defmodule IslandsInterface.Application do
  # See https://hexdocs.pm/elixir/Application.html
  # for more information on OTP Applications
  @moduledoc false

  use Application

  def start(_type, _args) do
    children = [
      # Start the Telemetry supervisor
      IslandsInterfaceWeb.Telemetry,
      # Start the PubSub system
      {Phoenix.PubSub, name: IslandsInterface.PubSub},
      # Start the Endpoint (http/https)
      IslandsInterfaceWeb.Endpoint
      # Start a worker by calling: IslandsInterface.Worker.start_link(arg)
      # {IslandsInterface.Worker, arg}
    ]

    # See https://hexdocs.pm/elixir/Supervisor.html
    # for other strategies and supported options
    opts = [strategy: :one_for_one, name: IslandsInterface.Supervisor]
    Supervisor.start_link(children, opts)
  end

  # Tell Phoenix to update the endpoint configuration
  # whenever the application is updated.
  def config_change(changed, _new, removed) do
    IslandsInterfaceWeb.Endpoint.config_change(changed, removed)
    :ok
  end
end
Communicating between players

We need to do all the ...