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. 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.
Currently, the following web servers are supported, and can be accessed directly or via HAProxy:
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.
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. = lambda do |event|
ws.send(event.data)
end
ws.onclose = lambda 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
This is a standard Rack app, so it can be run using a config.ru
file. However, so that incoming requests can be properly prepared to process WebSocket connections, you need to tell Faye::WebSocket
which adapter to load; this can be either thin
, rainbows
or goliath
. If one of these servers is already loaded before faye/websocket
is loaded, it will load appropriate adapters automatically.
# config.ru
require './app'
Faye::WebSocket.load_adapter('thin')
run App
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.onopen = lambda do |event|
p [:open]
ws.send('Hello, world!')
end
ws. = 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 aString
(for text frames) or anArray
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
andreason
, that expose the status code and message sent by the peer that closed the connection. -
send(message)
accepts either aString
or anArray
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 (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.onclose = lambda 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
:
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:
-
: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 => 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
To use this library you must be using an EventMachine-based server; currently Thin, Rainbows and Goliath are supported.
Running the app with 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'
EM.run {
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. = {
:private_key_file => 'path/to/ssl.key',
:cert_chain_file => 'path/to/ssl.crt'
}
server.ssl = true
end
}
Running the app with Rainbows
Faye::WebSocket
can only be run using EventMachine. To begin with, you’ll need a Rainbows config file that tells it to use EventMachine, along with whatever Rainbows/Unicorn configuration you require.
# rainbows.conf
Rainbows! do
use :EventMachine
end
You can then 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
Rainbows also has a Ruby API for starting a server:
require 'rainbows'
require './app'
rackup = Unicorn::Configurator::RACKUP
rackup[:port] = 9292
rackup[:set_listener] = true
= rackup[:options]
[:config_file] = 'path/to/rainbows.conf'
server = Rainbows::HttpServer.new(App, )
# This is non-blocking; use server.start.join to block
server.start
Running the app with 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'
class EchoServer < 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'
class EchoServer < Goliath::API
def response(env)
ws = Faye::WebSocket.new(env)
ws. = lambda do |event|
ws.send(event.data)
end
ws.rack_response
end
end
License
(The MIT License)
Copyright © 2009-2012 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.