Faye::WebSocket

This is a robust, 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 running under Thin. It does not provide any abstraction other than the standard WebSocket API.

The server-side socket can process draft-75, draft-76, hybi-07 and later versions of the protocol. It selects protocol versions automatically, supports both text and binary messages, and transparently handles ping, pong, close and fragmented messages.

Accepting WebSocket connections in Rack

You can handle WebSockets on the server side by listening for HTTP Upgrade requests, 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:

require 'faye/websocket'
require 'rack'
require 'eventmachine'

app = lambda do |env|
  if env['HTTP_UPGRADE']
    ws = Faye::WebSocket.new(env)

    ws.onmessage = lambda do |event|
      ws.send(event.data)
    end

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

    # Thin async response
    [-1, {}, []]

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

EM.run {
  thin = Rack::Handler.get('thin')
  thin.run(app, :Port => 9292)
}

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, though it’s compatible with servers speaking later versions of the protocol.

require 'faye/websocket'
require 'eventmachine'

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

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

  ws.onmessage = lambda do |event|
    p [:message, event.data]
  end

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

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. If they cannot agree on a protocol to use, the client closes the connection.

WebSocket API

The WebSocket API consists of several event handlers and a method for sending messages.

onopen fires when the socket connection is established. Event has no attributes.
onerror fires when the connection attempt fails. Event has no attributes.
onmessage 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).
onclose 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.
close(code, reason) closes the connection, sending the given status code and reason text, both of which are optional.
protocol is a string or nil identifying the subprotocol th socket is using.

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.