Standards-compliant WebSocket client and server
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.hijack API should also work.
$ gem install faye-websocket
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' => '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.
ws.ping 'Mic check, one, two' do
# fires when pong is received
end
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.
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:
ws = Faye::WebSocket::Client.new('ws://www.example.com/', [], {
:proxy => {
:origin => 'http://username:[email protected]',
:headers => { 'User-Agent' => 'ruby' }
}
})
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.
faye-websocket is based on the
websocket-extensions
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:
require 'permessage_deflate'
ws = Faye::WebSocket.new(env, [], :extensions => [PermessageDeflate])
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:
:extensions - an array of:headers - a hash containing key-value pairs representing HTTP headers to be:max_length - the maximum allowed size of incoming message frames, in bytes.2^26 - 1, or 1 byte short of 64 MiB.:ping - an integer that sets how often the WebSocket should send ping:tls - a hash containing key-value pairs for specifying TLS parameters.Starting with version 0.11.0, Faye::WebSocket::Client will verify the server
certificate for wss connections. This is not the default behaviour for
EventMachine’s TLS interface, and so our defaults for the :tls option are a
little different.
First, :verify_peer is enabled by default. Our implementation checks that the
chain of certificates sent by the server is trusted by your root certificates,
and that the final certificate’s hostname matches the hostname in the request
URL.
By default, we use your system’s root certificate store by invoking
OpenSSL::X509::Store#set_default_paths. If you want to use a different set of
root certificates, you can pass them via the :root_cert_file option, which
takes a path or an array of paths to the certificates you want to use.
ws = Faye::WebSocket::Client.new('wss://example.com/', [], :tls => {
:root_cert_file => ['path/to/certificate.pem']
})
If you want to switch off certificate verification altogether, then set
:verify_peer to false.
ws = Faye::WebSocket::Client.new('wss://example.com/', [], :tls => {
:verify_peer => false
})
Both the server- and client-side WebSocket objects support the following API:
on(:open) { |event| } fires when the socket connection is established.on(:message) { |event| } fires when the socket receives a message. Eventdata, which is either a String (for text frames) orArray of unsigned integers, i.e. integers in the range 0..255 (foron(:error) { |event| } fires when there is a protocol error due to badon(:close) { |event| } fires when either the client or the server closescode andreason, that expose the status code and message sent by the peer thatsend(message) accepts either a String or an Array of byte-sizedArray.ping(message, &callback) sends a ping frame with an optional message andclose(code, reason) closes the connection, sending the given status codeversion is a string containing the version of the WebSocket protocolprotocol is a string (which may be empty) identifying the subprotocolEventSource 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' => '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 thelast_event_id is a string containing the last event ID received by theWhen 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:retry is a number that tells the client how long (in seconds) it should:ping is a number that tells the server how often (in seconds) to sendFor 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:
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.
The following describes how to run a WebSocket application using all our
supported web servers.
If you use Thin to serve 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. You can configure Thin further in a block passed to run:
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
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.
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.
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.
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
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
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 < 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 < 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