User-level WebSocket support for Nex applications.

Provides bidirectional real-time communication via WebSocket connections. Built on top of WebSockAdapter (already a framework dependency).

Usage

Define a WebSocket handler in src/api/ using Nex.WebSocket:

defmodule MyApp.Api.Chat do
  use Nex.WebSocket

  def handle_connect(state) do
    {:ok, state}
  end

  def handle_message("ping", state) do
    {:reply, "pong", state}
  end

  def handle_message(msg, state) do
    {:reply, "echo: " <> msg, state}
  end

  def handle_disconnect(state) do
    {:ok, state}
  end
end

The module is automatically routed to /ws/chat (mirrors the API path convention). Connect from the browser:

const ws = new WebSocket("ws://localhost:4000/ws/chat");
ws.onmessage = (e) => console.log(e.data);
ws.send("ping");

Callbacks

• handle_connect/1 — called when a client connects. Return {:ok, state}.
• handle_message/2 — called for each incoming message. Return:
  • {:reply, message, state} — send a message back to the client
  • {:ok, state} — no reply
  • {:stop, reason, state} — close the connection
• handle_disconnect/1 — called when the client disconnects. Return {:ok, state}.

Initial State

Override initial_state/1 to set per-connection state from the request:

def initial_state(req) do
  %{user_id: Nex.Session.get(:user_id), joined_at: DateTime.utc_now()}
end

Broadcasting

Use Nex.WebSocket.broadcast/2 to send messages to all connected clients on a named topic (requires Phoenix.PubSub, already a framework dependency):

Nex.WebSocket.broadcast("chat", "New message!")

Subscribe in handle_connect/1:

def handle_connect(state) do
  Nex.WebSocket.subscribe("chat")
  {:ok, state}
end