Clients subscribe to the game to get updates

lib/chess_web/views/live/board_live.ex

@@ -14,6 +14,8 @@ defmodule ChessWeb.BoardLive do
   end
 
   def mount(_params, %{"user_id" => user_id, "game_id" => game_id}, socket) do
+    ChessWeb.Endpoint.subscribe("game:#{game_id}")
+
     user = Repo.get!(User, user_id)
 
     game =
@@ -40,6 +42,10 @@ defmodule ChessWeb.BoardLive do
     }
   end
 
+  def handle_info(%{event: "move", payload: state}, socket) do
+    {:noreply, assign(socket, state)}
+  end
+
   defp handle_click(socket, file, rank) do
     game = socket.assigns[:game]
     board = game.board
@@ -87,6 +93,8 @@ defmodule ChessWeb.BoardLive do
           {:ok, %{game: game}} ->
             board = Board.transform(game.board)
 
+            broadcast_move(game, board)
+
             [
               {:selected, nil},
               {:available, []},
@@ -98,4 +106,13 @@ defmodule ChessWeb.BoardLive do
       [{:selected, nil}, {:available, []}]
     end
   end
+
+  defp broadcast_move(game, board) do
+    ChessWeb.Endpoint.broadcast_from(
+      self(),
+      "game:#{game.id}",
+      "move",
+      %{game: game, board: board}
+    )
+  end
 end