WebSocket

An exploration into a stand-alone library for Plug applications to easily adopt WebSockets.

Viewing the examples

Run these:

$ git clone https://github.com/slogsdon/plug-web-socket
$ cd plug-web-socket
$ mix deps.get
$ iex -S mix run run_examples.exs

Go here: http://localhost:4000.

You will be presented with a list of possible examples/tests that use a WebSocket connection.

Integrating with Plug

If you’re looking to try this in your own test application, do something like this:

defmodule MyApp.Router do
  use Plug.Router
  use WebSocket

  # WebSocket routes
  #      route     controller/handler     function & name
  socket "/topic", MyApp.TopicController, :handle
  socket "/echo",  MyApp.EchoController,  :echo

  # Rest of your router's plugs and routes
  # ...

  def run(opts \\ []) do
    dispatch = dispatch_table(opts)
    Plug.Adapters.Cowboy.http __MODULE__, opts, [dispatch: dispatch]
  end
end

For the time being, there is a run/1 function generated for your router that starts a HTTP/WS listener. Not sure if this will stay or get reduced to helper functions that aid in the creation of a similar function. Most likely the latter will win out to help compose functionality. The big part that it plays is the building of a dispatch table to pass as an option to Cowboy that has an entry for each of your socket routes and a catch all for HTTP requests.

Add the necessary bits to a module

From the topic example:

defmodule MyApp.TopicController do
  def handle(:init, state) do
    {:ok, state}
  end
  def handle(:terminate, _state) do
    :ok
  end
  def handle("topic:" <> letter, state, data) do
    payload = %{awesome: "blah #{letter}",
                orig: data}
    {:reply, {:text, payload}, state}
  end
end

Currently, the function name needs to be unique across all controllers/handlers as its used for the Events layer.

Broadcast from elsewhere

Need to send data out from elsewhere in your app?

# Build your message
topic = "my_event"
data  = %{foo: "awesome"}
mes   = WebSocket.Message.build(topic, data)
json  = Poison.encode!(mes)

# Pick your destination (from your routes)
name = :handle

# Send away!
WebSockets.broadcast!(name, json)

This needs to be nicer, but this is still in progress.

License

WebSocket is released under the MIT License.

See LICENSE for details.