faye-websocket

Travis CI build:
Autobahn tests: server, client

This is a general-purpose WebSocket implementation extracted from the
Faye project. It provides classes for easily
building WebSocket servers and clients in Ruby. It does not provide a server
itself, but rather makes it easy to handle WebSocket connections within an
existing Rack application. It does not provide
any abstraction other than the standard WebSocket
API.

It also provides an abstraction for handling
EventSource connections, which are
one-way connections that allow the server to push data to the client. They are
based on streaming HTTP responses and can be easier to access via proxies than
WebSockets.

The following web servers are supported. Other servers that implement the
rack.hjiack API should also work.

Goliath
Phusion Passenger >= 4.0 with nginx >= 1.4
Puma >= 2.0
Rainbows
Thin

Installation

$ gem install faye-websocket

Handling WebSocket connections in Rack

You can handle WebSockets on the server side by listening for requests using
the Faye::WebSocket.websocket? method, and creating a new socket for the
request. This socket object exposes the usual WebSocket methods for receiving
and sending messages. For example this is how you’d implement an echo server:

# app.rb
require 'faye/websocket'

App = lambda do |env|
  if Faye::WebSocket.websocket?(env)
    ws = Faye::WebSocket.new(env)

    ws.on :message do |event|
      ws.send(event.data)
    end

    ws.on :close do |event|
      p [:close, event.code, event.reason]
      ws = nil
    end

    # Return async Rack response
    ws.rack_response

  else
    # Normal HTTP request
    [200, {'Content-Type' =&gt; 'text/plain'}, ['Hello']]
  end
end

Note that under certain circumstances (notably a draft-76 client connecting
through an HTTP proxy), the WebSocket handshake will not be complete after you
call Faye::WebSocket.new because the server will not have received the entire
handshake from the client yet. In this case, calls to ws.send will buffer the
message in memory until the handshake is complete, at which point any buffered
messages will be sent to the client.

If you need to detect when the WebSocket handshake is complete, you can use the
onopen event.

If the connection’s protocol version supports it, you can call ws.ping() to
send a ping message and wait for the client’s response. This method takes a
message string, and an optional callback that fires when a matching pong
message is received. It returns true iff a ping message was sent. If the
client does not support ping/pong, this method sends no data and returns
false.

ws.ping 'Mic check, one, two' do
  # fires when pong is received
end

Using the WebSocket client

The client supports both the plain-text ws protocol and the encrypted wss
protocol, and has exactly the same interface as a socket you would use in a web
browser. On the wire it identifies itself as hybi-13.

require 'faye/websocket'
require 'eventmachine'

EM.run {
  ws = Faye::WebSocket::Client.new('ws://www.example.com/')

  ws.on :open do |event|
    p [:open]
    ws.send('Hello, world!')
  end

  ws.on :message do |event|
    p [:message, event.data]
  end

  ws.on :close do |event|
    p [:close, event.code, event.reason]
    ws = nil
  end
}

The WebSocket client also lets you inspect the status and headers of the
handshake response via its status and headers methods.

Subprotocol negotiation

The WebSocket protocol allows peers to select and identify the application
protocol to use over the connection. On the client side, you can set which
protocols the client accepts by passing a list of protocol names when you
construct the socket:

ws = Faye::WebSocket::Client.new('ws://www.example.com/', ['irc', 'amqp'])

On the server side, you can likewise pass in the list of protocols the server
supports after the other constructor arguments:

ws = Faye::WebSocket.new(env, ['irc', 'amqp'])

If the client and server agree on a protocol, both the client- and server-side
socket objects expose the selected protocol through the ws.protocol property.

Initialization options

Both the server- and client-side classes allow an options hash to be passed in
at initialization time, for example:

ws = Faye::WebSocket.new(env, protocols, options)
ws = Faye::WebSocket::Client.new(url, protocols, options)

protocols as an array of subprotocols as described above, or nil. options
is an optional hash containing any of these keys:

:headers - a hash containing key-value pairs representing HTTP headers to be sent during the handshake process
:ping - an integer that sets how often the WebSocket should send ping frames, measured in seconds

WebSocket API

Both the server- and client-side WebSocket objects support the following API:

on(:open) { |event| } fires when the socket connection is established. Event has no attributes.
onerror fires when the connection attempt fails. Event has no attributes.
on(:message) { |event| } fires when the socket receives a message. Event has one attribute, data, which is either a String (for text frames) or an Array of byte-sized integers (for binary frames).
on(:error) { |event| } fires when there is a protocol error due to bad data sent by the other peer. This event is purely informational, you do not need to implement error recovery.
on(:close) { |event| } fires when either the client or the server closes the connection. Event has two optional attributes, code and reason, that expose the status code and message sent by the peer that closed the connection.
send(message) accepts either a String or an Array of byte-sized integers and sends a text or binary message over the connection to the other peer.
ping(message = '', &callback) sends a ping frame with an optional message and fires the callback when a matching pong is received.
close closes the connection.
version is a string containing the version of the WebSocket protocol the connection is using.
protocol is a string (which may be empty) identifying the subprotocol the socket is using.

Handling EventSource connections in Rack

EventSource connections provide a very similar interface, although because they
only allow the server to send data to the client, there is no onmessage API.
EventSource allows the server to push text messages to the client, where each
message has an optional event-type and ID.

# app.rb
require 'faye/websocket'

App = lambda do |env|
  if Faye::EventSource.eventsource?(env)
    es = Faye::EventSource.new(env)
    p [:open, es.url, es.last_event_id]

    # Periodically send messages
    loop = EM.add_periodic_timer(1) { es.send('Hello') }

    es.on :close do |event|
      EM.cancel_timer(loop)
      es = nil
    end

    # Return async Rack response
    es.rack_response

  else
    # Normal HTTP request
    [200, {'Content-Type' =&gt; 'text/plain'}, ['Hello']]
  end
end

The send method takes two optional parameters, :event and :id. The
default event-type is 'message' with no ID. For example, to send a
notification event with ID 99:

es.send('Breaking News!', :event =&gt; 'notification', :id =&gt; '99')

The EventSource object exposes the following properties:

url is a string containing the URL the client used to create the EventSource.
last_event_id is a string containing the last event ID received by the client. You can use this when the client reconnects after a dropped connection to determine which messages need resending.

When you initialize an EventSource with Faye::EventSource.new, you can pass
configuration options after the env parameter. Available options are:

:retry is a number that tells the client how long (in seconds) it should wait after a dropped connection before attempting to reconnect.
:ping is a number that tells the server how often (in seconds) to send ‘ping’ packets to the client to keep the connection open, to defeat timeouts set by proxies. The client will ignore these messages.

For example, this creates a connection that pings every 15 seconds and is
retryable every 10 seconds if the connection is broken:

es = Faye::EventSource.new(es, :ping =&gt; 15, :retry =&gt; 10)

You can send a ping message at any time by calling es.ping. Unlike WebSocket
the client does not send a response to this; it is merely to send some data
over the wire to keep the connection alive.

Running your socket application

The following describes how to run a WebSocket application using all our
supported web servers.

Running the app with Thin

If you use Thin to server your application you need to include this line after
loading faye/websocket:

Faye::WebSocket.load_adapter('thin')

Thin can be started via the command line if you’ve set up a config.ru file
for your application:

$ thin start -R config.ru -p 9292

Or, you can use rackup. In development mode, this adds middlewares that don’t
work with async apps, so you must start it in production mode:

$ rackup config.ru -s thin -E production -p 9292

It can also be started using the Rack::Handler interface common to many Ruby
servers. It must be run using EventMachine, and you can configure Thin further
in a block passed to run:

require 'eventmachine'
require 'rack'
require 'thin'
require './app'

Faye::WebSocket.load_adapter('thin')

EM.run {
  thin = Rack::Handler.get('thin')

  thin.run(App, :Port =&gt; 9292) do |server|
    # You can set options on the server here, for example to set up SSL:
    server.ssl_options = {
      :private_key_file =&gt; 'path/to/ssl.key',
      :cert_chain_file  =&gt; 'path/to/ssl.crt'
    }
    server.ssl = true
  end
}

Running the app with Passenger

faye-websocket requires either Passenger for Nginx or Passenger Standalone.
Apache doesn’t work well with WebSockets at this time. You do not need any
special configuration to make faye-websocket work, it should work out of the
box on Passenger provided you use at least Passenger 4.0.

Run your app on Passenger for Nginx by creating a virtual host entry which
points to your app’s “public” directory:

server {
  listen 9292;
  server_name yourdomain.local;
  root /path-to-your-app/public;
  passenger_enabled on;
}

Or run your app on Passenger Standalone:

$ passenger start -p 9292

More information can be found on the Passenger
website.

Running the app with Puma

Puma has a command line interface for starting your application:

$ puma config.ru -p 9292

Running the app with Rainbows

If you’re using version 4.4 or lower of Rainbows, you need to run it with the
EventMachine backend and enable the adapter. Put this in your rainbows.conf
file:

Rainbows! { use :EventMachine }

And make sure you load the adapter in your application:

Faye::WebSocket.load_adapter('rainbows')

Version 4.5 of Rainbows does not need this adapter.

You can run your config.ru file from the command line. Again, Rack::Lint
will complain unless you put the application in production mode.

$ rainbows config.ru -c path/to/rainbows.conf -E production -p 9292

Running the app with Goliath

If you use Goliath to server your application you need to include this line
after loading faye/websocket:

Faye::WebSocket.load_adapter('goliath')

Goliath can be made to run arbitrary Rack apps by delegating to them from a
Goliath::API instance. A simple server looks like this:

require 'goliath'
require './app'
Faye::WebSocket.load_adapter('goliath')

class EchoServer &lt; Goliath::API
  def response(env)
    App.call(env)
  end
end

Faye::WebSocket can also be used inline within a Goliath app:

require 'goliath'
require 'faye/websocket'
Faye::WebSocket.load_adapter('goliath')

class EchoServer &lt; Goliath::API
  def response(env)
    ws = Faye::WebSocket.new(env)

    ws.on :message do |event|
      ws.send(event.data)
    end

    ws.rack_response
  end
end

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the ‘Software’), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Modules

Classes