# faye-websocket

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* Autobahn tests: [server](http://faye.jcoglan.com/autobahn/servers/),
  [client](http://faye.jcoglan.com/autobahn/clients/)

This is a general-purpose WebSocket implementation extracted from the
[Faye](http://faye.jcoglan.com) 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](http://rack.github.io/) application. It does not provide any abstraction
other than the standard [WebSocket
API](https://html.spec.whatwg.org/multipage/comms.html#network).

It also provides an abstraction for handling
[EventSource](https://html.spec.whatwg.org/multipage/comms.html#server-sent-events)
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.hijack` API should also work.

* [Goliath](http://postrank-labs.github.com/goliath/)
* [Phusion Passenger](https://www.phusionpassenger.com/) >= 4.0 with nginx >= 1.4
* [Puma](http://puma.io/) >= 2.0
* [Rainbows](http://rainbows.bogomips.org/)
* [Thin](http://code.macournoyer.com/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:

```ruby
# 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' => '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` if and only if a ping message was sent. If the
client does not support ping/pong, this method sends no data and returns
`false`.

```ruby
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`.

```ruby
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.

To connect via a proxy, set the `proxy` option to the HTTP origin of the proxy,
including any authorization information and custom headers you require:

```rb
ws = Faye::WebSocket::Client.new('ws://www.example.com/', [], {
  :proxy => {
    :origin  => 'http://username:password@proxy.example.com',
    :headers => {'User-Agent' => 'ruby'}
  }
})
```


## 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:

```ruby
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:

```ruby
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.


## Protocol extensions

faye-websocket is based on the
[websocket-extensions](https://github.com/faye/websocket-extensions-ruby)
framework that allows extensions to be negotiated via the
`Sec-WebSocket-Extensions` header. To add extensions to a connection, pass an
array of extensions to the `:extensions` option. For example, to add
[permessage-deflate](https://github.com/faye/permessage-deflate-ruby):

```rb
require 'permessage_deflate'

ws = Faye::WebSocket.new(env, [], :extensions => [PermessageDeflate])
```


## Initialization options

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

```ruby
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:

* `:extensions` - an array of
  [websocket-extensions](https://github.com/faye/websocket-extensions-ruby)
  compatible extensions, as described above
* `:headers` - a hash containing key-value pairs representing HTTP headers to be
  sent during the handshake process
* `:max_length` - the maximum allowed size of incoming message frames, in bytes.
  The default value is `2^26 - 1`, or 1 byte short of 64 MiB.
* `:ping` - an integer that sets how often the WebSocket should send ping
  frames, measured in seconds
* `:tls` - a hash containing key-value pairs for specifying TLS parameters.
  These are passed along to EventMachine and you can find
  [more details here](http://rubydoc.info/gems/eventmachine/EventMachine%2FConnection%3Astart_tls)

## 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.
* `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; binary data must be encoded as an `Array`.
* `ping(message, &callback)` sends a ping frame with an optional message
  and fires the callback when a matching pong is received.
* `close(code, reason)` closes the connection, sending the given status
  code and reason text, both of which are optional.
* `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.

```ruby
# 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' => '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`:

```ruby
es.send('Breaking News!', :event => 'notification', :id => '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:

* `:headers` is a hash containing custom headers to be set on the
  EventSource response.
* `: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 allows access from any origin, pings
every 15 seconds and is retryable every 10 seconds if the connection is broken:

```ruby
es = Faye::EventSource.new(es,
  :headers => {'Access-Control-Allow-Origin' => '*'},
  :ping    => 15,
  :retry   => 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 serve your application you need to include this line after
loading `faye/websocket`:

```ruby
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. You can configure Thin further in a block passed to `run`:

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

Faye::WebSocket.load_adapter('thin')

thin = Rack::Handler.get('thin')

thin.run(App, :Port => 9292) do |server|
  # You can set options on the server here, for example to set up SSL:
  server.ssl_options = {
    :private_key_file => 'path/to/ssl.key',
    :cert_chain_file  => '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](https://github.com/phusion/passenger/issues/1202).
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.

However, you do need to insert the following code in `config.ru` for optimal
WebSocket performance in Passenger. This is
[documented in the Passenger manual](https://www.phusionpassenger.com/documentation/Users%20guide%20Nginx.html#tuning_sse_websockets).

```ruby
if defined?(PhusionPassenger)
  PhusionPassenger.advertised_concurrency_level = 0
end
```

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](https://www.phusionpassenger.com/support).


### Running the app with Puma

Puma has a command line interface for starting your application:

```
$ puma 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 puma -E production -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:

```ruby
Rainbows! { use :EventMachine }
```

And make sure you load the adapter in your application:

```ruby
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`:

```ruby
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:

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

class EchoServer < Goliath::API
  def response(env)
    App.call(env)
  end
end
```

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

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

class EchoServer < 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)

Copyright (c) 2010-2017 James Coglan

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.
