Add channel to be joined

lib/birdy_chat_web/channels/server_channel.ex

@@ -0,0 +1,35 @@
+defmodule BirdyChatWeb.ServerChannel do
+  use BirdyChatWeb, :channel
+
+  @impl true
+  def join("server:" <> server_id, payload, socket) do
+    if authorised?(payload, server_id) do
+      {:ok, socket}
+    else
+      {:error, %{reason: "unauthorised"}}
+    end
+  end
+
+  @impl true
+  def handle_in("new_message", {:binary, message}, socket) do
+    result = :erlang.binary_to_term(message, [:safe])
+
+    # TODO: Add validation that this is the right server.
+    case BirdyChat.Message.validate(result) do
+      {:ok, changeset} ->
+        case BirdyChat.MessageWriter.write(changeset.changes) do
+          :ok ->
+            {:reply, {:ok, {:binary, message}}, socket}
+        end
+    end
+  end
+
+  # Simple token-based authentication. Servers should use the same Phoenix secret key so they will
+  # have the basis for generating tokens.
+  defp authorised?(%{"token" => token}, server_id) do
+    case Phoenix.Token.verify(BirdyChatWeb.Endpoint, "serverAuth", token, max_age: 86400) do
+      {:ok, id} -> id == server_id
+      {:error, :invalid} -> false
+    end
+  end
+end

lib/birdy_chat_web/channels/server_socket.ex

@@ -0,0 +1,44 @@
+defmodule BirdyChatWeb.ServerSocket do
+  use Phoenix.Socket
+
+  # A Socket handler
+  #
+  # It's possible to control the websocket connection and
+  # assign values that can be accessed by your channel topics.
+
+  ## Channels
+
+  channel "server:*", BirdyChatWeb.ServerChannel
+
+  # Socket params are passed from the client and can
+  # be used to verify and authenticate a user. After
+  # verification, you can put default assigns into
+  # the socket that will be set for all channels, ie
+  #
+  #     {:ok, assign(socket, :user_id, verified_user_id)}
+  #
+  # To deny connection, return `:error` or `{:error, term}`. To control the
+  # response the client receives in that case, [define an error handler in the
+  # websocket
+  # configuration](https://hexdocs.pm/phoenix/Phoenix.Endpoint.html#socket/3-websocket-configuration).
+  #
+  # See `Phoenix.Token` documentation for examples in
+  # performing token verification on connect.
+  @impl true
+  def connect(_params, socket, _connect_info) do
+    {:ok, socket}
+  end
+
+  # Socket IDs are topics that allow you to identify all sockets for a given user:
+  #
+  #     def id(socket), do: "user_socket:#{socket.assigns.user_id}"
+  #
+  # Would allow you to broadcast a "disconnect" event and terminate
+  # all active sockets and channels for a given user:
+  #
+  #     Elixir.BirdyChatWeb.Endpoint.broadcast("user_socket:#{user.id}", "disconnect", %{})
+  #
+  # Returning `nil` makes this socket anonymous.
+  @impl true
+  def id(socket), do: "user_socket:#{socket.assigns.server_id}"
+end

lib/birdy_chat_web/endpoint.ex

@@ -15,6 +15,10 @@ defmodule BirdyChatWeb.Endpoint do
     websocket: [connect_info: [session: @session_options]],
     longpoll: [connect_info: [session: @session_options]]
 
+  socket "/socket", BirdyChatWeb.ServerSocket,
+    websocket: true,
+    longpoll: false
+
   # Serve at "/" the static files from "priv/static" directory.
   #
   # When code reloading is disabled (e.g., in production),