I'm switching over from ActionController:Live to websocket-rails, and I was just wondering how to close the connection on the server side once the user closes the browser window?
With ActionController:Live I used to have:
def stream
response.headers['Content-Type'] = 'text/event-stream'
#redis_sub = RedisStream.new_redis_client
# Subscribing to user's stream by session token
#redis_sub.subscribe([ token ]) do |on|
on.message do |channel, msg|
## Did stuff
response.stream.write(msg)
end
end
rescue IOError
"\n\nIOError in controller"
rescue ClientDisconnected
puts "\n\nClient has disconnected\n\n"
ensure
#redis_sub.quit
response.stream.close
end
And this worked fine, now I'm trying to do the same thing as this but using websockets, and I was wondering how to close the connection and quit out of my redis subscription.
connection.close! from within the websocket controller.
https://github.com/websocket-rails/websocket-rails/issues/219
To deepen a little in #TheNastyOne answer, you can close socket a connection from dispatcher on client side like this:
// Open connection.
var dispatcher = new WebSocketRails('localhost:3000/websocket');
// Close connection.
dispatcher.disconnect();
Here lives the issue that describe both methods.
Related
A common way to handle authentication/authorization of websocket connections is to use cookie sent on initial http upgrade request. This is shown here http://edgeguides.rubyonrails.org/action_cable_overview.html
But what if I don't want to use cookie, but rather a token? Couple of hacks discussed here Send auth_token for authentication to ActionCable but it's too hacky imo.
What if I move the token authorization logic to channel:
module ApplicationCable
class Connection < ActionCable::Connection::Base
identified_by :connection_id
def connect
self.connection_id = SecureRandom.hex # accept anyone, identify by random string
end
end
end
This will accept any connection. And than:
class TestChannel < ApplicationCable::Channel
def subscribed
if authorize(params[:token]) # check the token here
stream_from "test:1"
else
connection.close # alternatively `reject_subscription` to keep ws connection open
end
end
def unsubscribed
stop_all_streams
end
end
Frontend subscription will look like this
App.test = App.cable.subscriptions.create(channel: "TestChannel", token: "hello-world")
This seems to work. The individual connection is identified by a random string and each channel subscription holds this unique connection. When broadcast to this channel is made it will push the data to all subscribers through their unique connections. So if we rejected a subscriber here it won't receive anything. But we cannot close unauthorized connections before subscription attempt. I can just open the connection to /cable and hold it as long as I want.
But is this safe? The obvious problem here is that anybody can open as many ws connection as he like. Is this the only problem with such approach?
I'm trying to setup a script written in ruby to open a port 2004 on a server. Called the server with http and the port http://<server>:2004/ will then result back a HTTP header + response.
The response is read from a file.
This is working for small content, but not for like 50MB.
Somehow it simply breaks.
By the way I'm testing this script with SoapUI.
Here is the source code, I think this one is pretty self-explanatory.
For better reading I marked the response part big.
#!/bin/ruby
require 'socket'
require 'timeout'
require 'date'
server = TCPServer.open 2004
puts "Listening on port 2004"
#file="dump.request"
loop {
Thread.start(server.accept) do |client|
date = Time.now.strftime("%d-%m-%Y_%H-%M-%S")
file = "#{date}_mt_dump.txt"
puts date
puts "Accepting connection"
#client = server.accept
#resp = "OKY|So long and thanks for all the fish!|OKY"
ticket_id = "1235"
partial_data = ""
i = 1024
firstrun = "yes"
fd = File.open(file,'w')
puts "Attempting receive loop"
puts "Ready to transfer contents to the client"
f = File.open("output.txt.gz","r")
puts "Opened file output.txt.gz; size: #{f.size}"
resp = f.read(f.size)
headers = ["HTTP/1.1 200 OK",
"Content-Encoding: gzip",
"Content-Type: text/xml;charset=UTF-8",
"Content-Length: #{f.size}\r\n\r\n"].join("\r\n")
client.puts headers
#puts all_data.join()
fd.close unless fd == nil
puts "Start data transfer"
client.puts resp
client.close
puts "Closed connection"
puts "\n"
end
}
There are a number of issues I see with your code, some which are conceptual and some of which are technical, but without more information about the error you receive might be impossible to offer a correct response.
It is my initial thought that the issue is caused by the fact that you are opening Gzipped files without using the binary mode flag, so that the file reading stops ate the first EOF character and new line markers might be converted.
A few technical things to consider:
Your loop is infinite. You should really set up signal traps to allow you to exit the script (catching ^C, for example).
Zip files are usually binary files. You should use a binary mode to open the file, or use the IO.binread method if your loading the whole file up to memory.
Your loading the whole file unto the memory before sending it. That's great for small files, but it isn't the best approach for larger files. Loading 50MB up to the RAM for each client, while serving a 100 clients, means 5GB of RAM...
Considering the first two technical points, I would tweek the code a bit like so:
keep_running = true
trap('INT'){ keep_running = false ; raise ::SystemExit}
begin
while(run) {
Thread.start(server.accept) do |client|
date = Time.now.strftime("%d-%m-%Y_%H-%M-%S")
file = "#{date}_mt_dump.txt"
puts date
puts "Accepting connection"
#client = server.accept
#resp = "OKY|So long and thanks for all the fish!|OKY"
ticket_id = "1235"
partial_data = ""
i = 1024
firstrun = "yes"
fd = File.open(file,'bw')
puts "Attempting receive loop"
puts "Ready to transfer contents to the client"
f = File.open("output.txt.gz","br")
puts "Opened file output.txt.gz; size: #{f.size}"
resp = f.read(f.size)
headers = ["HTTP/1.1 200 OK",
"Content-Encoding: gzip",
"Content-Type: text/xml;charset=UTF-8",
"Content-Length: #{f.size}\r\n\r\n"].join("\r\n")
client.puts headers
#puts all_data.join()
fd.close unless fd == nil
puts "Start data transfer"
client.puts resp
client.close
puts "Closed connection"
puts "\n"
end
}
rescue => e
puts e.message
puts e.backtrace
rescue SystemExit => e
puts "exiting... please notice that existing threads will be brutally stoped, as we will not wait for them..."
end
As to my more general pointers:
Your code is opening a new thread per connection. While this is okay for a small load of concurrent connections, your script might grind to a halt if you have a lot of concurrent connections. The context-switching alone (moving between threads) could potentially create a DoS situation.
I recommend that you use a Reactor pattern, where you have a pool of threads. Another option is to fork a few processes listening to the same TCPSocket.
You don't read the data from the socket and you don't parse the HTTP request - this means that someone could potentially fill up the system buffer, which you never empty, by continuously sendings data.
It would be better if you read the information from the socket, or emptied it's buffer, as well as disconnected from any malformed of malicious connections.
Also, most browsers aren't too happy when the response comes in before the request...
You don't catch any exceptions nor print any error messages. This means that your script might throw an exception that will break everything apart. For instance, if your 'server' will reach the 'open file limit' for it's process, the accept method will throw an exception which will shut down the whole script, including existing connections.
I'm not sure why you aren't using one of the many HTTP servers available for Ruby - be it the builtin WEBrick (don't use for production) or one of the native Ruby community gems, such as Iodine.
Here's a short example using Iodine, which has an easy to utilize Http server written in Ruby (no need to compile anything):
require 'iodine/http'
# cache the file, since it's the only response ever sent
file_data = IO.binread "output.txt.gz"
Iodine.on_http do |request, response|
begin
# set any headers
response['content-type'] = 'text/xml;charset=UTF-8'
response['content-encoding'] = 'gzip'
response << file_data
true
rescue => e
Iodine.error e
false
end
end
end
#if in irb:
exit
Or, if you insist on writing your own HTTP server, you can at least use a one of the available IO reactors, such as Iodine (I it wrote for Plezi), to help you handle the thread pool and IO management (you can also use EventMachine, but I don't it like so much - than again, I'm biased, as I wrote the Iodine Library):
require 'iodine'
require 'stringio'
class MiniServer < Iodine::Protocol
# cache the file, since it's the only data sent,
# and make it available to all the connections.
def self.data
#data ||= IO.binread 'output.txt.gz'
end
# The on_opne callback is called when a connection is established.
# We'll use it to initialize the HTTP request's headers Hash.
def on_open
#headers = {}
end
# the on_message callback is called when data is sent from the client to the socket.
def on_message input
input = StringIO.new input
l = nil
headers = #headers # easy access
# loop the lines and parse the HTTP request.
while (l = input.gets)
unless l.match /^[\r]?\n/
if l.include? ':'
l = l.strip.downcase.split(':', 2)
headers[l[0]] = l[1]
else
headers[:method], headers[:query], headers[:version] = l.strip.split(/[\s]+/, 3)
headers[:request_start] = Time.now
end
next
end
# keep the connection alive if the HTTP version is 1.1 or if the connection is requested to be kept alive
keep_alive = (headers['connection'].to_s.match(/keep/i) || headers[:version].match(/1\.1/)) && true
# refuse any file uploads or forms. make sure the request is a GET request
return close if headers['content-length'] || headers['content-type'] || headers[:method].to_s.match(/get/i).nil?
# all is well, send the file.
write ["HTTP/1.1 200 OK",
"Connection: #{keep_alive ? 'keep-alive' : 'close'}",
"Content-Encoding: gzip",
"Content-Type: text/xml;charset=UTF-8",
"Content-Length: #{self.class.data.bytesize}\r\n\r\n"].join("\r\n")
write self.class.data
return close unless keep_alive
# reset the headers, in case another request comes in
headers.clear
end
end
end
Iodine.protocol = MiniServer
# # if running within a larget application, consider:
# Iodine.force_start!
# # Server starts automatically when the script ends.
# # on irb, use `exit`:
exit
Good Luck!
#server = TCPServer.new('', 2001)
Thread.new do
loop do
puts 'loop iteration'
Thread.start(#server.accept) do |client|
puts 'in thread'
client.puts Time.now
puts client.read
client.close #This is the line I don't like
end
end
end
How to prevent connection closing and accept data from client without reconnects?
If I comment client.close out the server executes contents in thread only once, immediately after client connects and that's all.
Can u also post your client code?
I suppose this is happening because you just read only one message from the client till the end with client.read and than not doing any other reads on this connections.
If you close it, your client might be just reconnection and then new TCPSocket is created by the TCPServer.
If you are not accepting the client to send any more messages immidiatly, it's perfectly fine to close the connection.
This is what an AcceptSocket (TCPServer) is for. It allows you to save ressources, by not
having a running Thread to do polling for incoming messages.
If you do expect the client to send more messages in relativly short periods you should also have a loop in you Thread which is listening on a TCPSocket.
Thread.start(#server.accept) do |client|
puts 'in thread'
client.puts Time.now
loop do
puts client.gets #or client.read
end
end
See also ruby-tcp-chat Server#listen_user_messages
But then i guess you will need some timeout mechanism, which closes the connection if there have been no messages for some period of time, otherwise you end up with a lot of permanent running threads
Background: We've built a chat feature in to one of our existing Rails applications. We're using the new ActionController::Live module and running Puma (with Nginx in production), and subscribing to messages through Redis. We're using EventSource client side to establish the connection asynchronously.
Problem Summary: Threads are never dying when the connection is terminated.
For example, should the user navigate away, close the browser, or even go to a different page within the application, a new thread is spawned (as expected), but the old one continues to live.
The problem as I presently see it is that when any of these situations occur, the server has no way of knowing whether the connection on the browser's end is terminated, until something attempts to write to this broken stream, which would never happen once the browser has moved away from the original page.
This problem seems to be documented on github, and similar questions are asked on StackOverflow here (pretty well exact same question) and here (regarding getting number of active threads).
The only solution I've been able to come up with, based on these posts, is to implement a type of thread / connection poker. Attempting to write to a broken connection generates an IOError which I can catch and properly close the connection, allowing the thread to die. This is the controller code for that solution:
def events
response.headers["Content-Type"] = "text/event-stream"
stream_error = false; # used by flusher thread to determine when to stop
redis = Redis.new
# Subscribe to our events
redis.subscribe("message.create", "message.user_list_update") do |on|
on.message do |event, data| # when message is received, write to stream
response.stream.write("messageType: '#{event}', data: #{data}\n\n")
end
# This is the monitor / connection poker thread
# Periodically poke the connection by attempting to write to the stream
flusher_thread = Thread.new do
while !stream_error
$redis.publish "message.create", "flusher_test"
sleep 2.seconds
end
end
end
rescue IOError
logger.info "Stream closed"
stream_error = true;
ensure
logger.info "Events action is quitting redis and closing stream!"
redis.quit
response.stream.close
end
(Note: the events method seems to get blocked on the subscribe method invocation. Everything else (the streaming) works properly so I assume this is normal.)
(Other note: the flusher thread concept makes more sense as a single long-running background process, a bit like a garbage thread collector. The problem with my implementation above is that a new thread is spawned for each connection, which is pointless. Anyone attempting to implement this concept should do it more like a single process, not so much as I've outlined. I'll update this post when I successfully re-implement this as a single background process.)
The downside of this solution is that we've only delayed or lessened the problem, not completely solved it. We still have 2 threads per user, in addition to other requests such as ajax, which seems terrible from a scaling perspective; it seems completely unattainable and impractical for a larger system with many possible concurrent connections.
I feel like I am missing something vital; I find it somewhat difficult to believe that Rails has a feature that is so obviously broken without implementing a custom connection-checker like I have done.
Question: How do we allow the connections / threads to die without implementing something corny such as a 'connection poker', or garbage thread collector?
As always let me know if I've left anything out.
Update
Just to add a bit of extra info: Huetsch over at github posted this comment pointing out that SSE is based on TCP, which normally sends a FIN packet when the connection is closed, letting the other end (server in this case) know that its safe to close the connection. Huetsch points out that either the browser is not sending that packet (perhaps a bug in the EventSource library?), or Rails is not catching it or doing anything with it (definitely a bug in Rails, if that's the case). The search continues...
Another Update
Using Wireshark, I can indeed see FIN packets being sent. Admittedly, I am not very knowledgeable or experienced with protocol level stuff, however from what I can tell, I definitely detect a FIN packet being sent from the browser when I establish the SSE connection using EventSource from the browser, and NO packet sent if I remove that connection (meaning no SSE). Though I'm not terribly up on my TCP knowledge, this seems to indicate to me that the connection is indeed being properly terminated by the client; perhaps this indicates a bug in Puma or Rails.
Yet another update
#JamesBoutcher / boutcheratwest(github) pointed me to a discussion on the redis website regarding this issue, specifically in regards to the fact that the .(p)subscribe method never shuts down. The poster on that site pointed out the same thing that we've discovered here, that the Rails environment is never notified when the client-side connection is closed, and therefore is unable to execute the .(p)unsubscribe method. He inquires about a timeout for the .(p)subscribe method, which I think would work as well, though I'm not sure which method (the connection poker I've described above, or his timeout suggestion) would be a better solution. Ideally, for the connection poker solution, I'd like to find a way to determine whether the connection is closed on the other end without writing to the stream. As it is right now, as you can see, I have to implement client-side code to handle my "poking" message separately, which I believe is obtrusive and goofy as heck.
A solution I just did (borrowing a lot from #teeg) which seems to work okay (haven't failure tested it, tho)
config/initializers/redis.rb
$redis = Redis.new(:host => "xxxx.com", :port => 6379)
heartbeat_thread = Thread.new do
while true
$redis.publish("heartbeat","thump")
sleep 30.seconds
end
end
at_exit do
# not sure this is needed, but just in case
heartbeat_thread.kill
$redis.quit
end
And then in my controller:
def events
response.headers["Content-Type"] = "text/event-stream"
redis = Redis.new(:host => "xxxxxxx.com", :port => 6379)
logger.info "New stream starting, connecting to redis"
redis.subscribe(['parse.new','heartbeat']) do |on|
on.message do |event, data|
if event == 'parse.new'
response.stream.write("event: parse\ndata: #{data}\n\n")
elsif event == 'heartbeat'
response.stream.write("event: heartbeat\ndata: heartbeat\n\n")
end
end
end
rescue IOError
logger.info "Stream closed"
ensure
logger.info "Stopping stream thread"
redis.quit
response.stream.close
end
I'm currently making an app that revolves around ActionController:Live, EventSource and Puma and for those that are encountering problems closing streams and such, instead of rescuing an IOError, in Rails 4.2 you need to rescue ClientDisconnected. Example:
def stream
#Begin is not required
twitter_client = Twitter::Streaming::Client.new(config_params) do |obj|
# Do something
end
rescue ClientDisconnected
# Do something when disconnected
ensure
# Do something else to ensure the stream is closed
end
I found this handy tip from this forum post (all the way at the bottom): http://railscasts.com/episodes/401-actioncontroller-live?view=comments
Here's a potentially simpler solution which does not use a heartbeat. After much research and experimentation, here's the code I'm using with sinatra + sinatra sse gem (which should be easily adapted to Rails 4):
class EventServer < Sinatra::Base
include Sinatra::SSE
set :connections, []
.
.
.
get '/channel/:channel' do
.
.
.
sse_stream do |out|
settings.connections << out
out.callback {
puts 'Client disconnected from sse';
settings.connections.delete(out);
}
redis.subscribe(channel) do |on|
on.subscribe do |channel, subscriptions|
puts "Subscribed to redis ##{channel}\n"
end
on.message do |channel, message|
puts "Message from redis ##{channel}: #{message}\n"
message = JSON.parse(message)
.
.
.
if settings.connections.include?(out)
out.push(message)
else
puts 'closing orphaned redis connection'
redis.unsubscribe
end
end
end
end
end
The redis connection blocks on.message and only accepts (p)subscribe/(p)unsubscribe commands. Once you unsubscribe, the redis connection is no longer blocked and can be released by the web server object which was instantiated by the initial sse request. It automatically clears when you receive a message on redis and sse connection to the browser no longer exists in the collection array.
Building on #James Boutcher, I used the following in clustered Puma with 2 workers, so that I have only 1 thread created for the heartbeat in config/initializers/redis.rb:
config/puma.rb
on_worker_boot do |index|
puts "worker nb #{index.to_s} booting"
create_heartbeat if index.to_i==0
end
def create_heartbeat
puts "creating heartbeat"
$redis||=Redis.new
heartbeat = Thread.new do
ActiveRecord::Base.connection_pool.release_connection
begin
while true
hash={event: "heartbeat",data: "heartbeat"}
$redis.publish("heartbeat",hash.to_json)
sleep 20.seconds
end
ensure
#no db connection anyway
end
end
end
Here you are solution with timeout that will exit blocking Redis.(p)subscribe call and kill unused connection tread.
class Stream::FixedController < StreamController
def events
# Rails reserve a db connection from connection pool for
# each request, lets put it back into connection pool.
ActiveRecord::Base.clear_active_connections!
# Last time of any (except heartbeat) activity on stream
# it mean last time of any message was send from server to client
# or time of setting new connection
#last_active = Time.zone.now
# Redis (p)subscribe is blocking request so we need do some trick
# to prevent it freeze request forever.
redis.psubscribe("messages:*", 'heartbeat') do |on|
on.pmessage do |pattern, event, data|
# capture heartbeat from Redis pub/sub
if event == 'heartbeat'
# calculate idle time (in secounds) for this stream connection
idle_time = (Time.zone.now - #last_active).to_i
# Now we need to relase connection with Redis.(p)subscribe
# chanel to allow go of any Exception (like connection closed)
if idle_time > 4.minutes
# unsubscribe from Redis because of idle time was to long
# that's all - fix in (almost)one line :)
redis.punsubscribe
end
else
# save time of this (last) activity
#last_active = Time.zone.now
end
# write to stream - even heartbeat - it's sometimes chance to
# capture dissconection error before idle_time
response.stream.write("event: #{event}\ndata: #{data}\n\n")
end
end
# blicking end (no chance to get below this line without unsubscribe)
rescue IOError
Logs::Stream.info "Stream closed"
rescue ClientDisconnected
Logs::Stream.info "ClientDisconnected"
rescue ActionController::Live::ClientDisconnected
Logs::Stream.info "Live::ClientDisconnected"
ensure
Logs::Stream.info "Stream ensure close"
redis.quit
response.stream.close
end
end
You have to use reds.(p)unsubscribe to end this blocking call. No exception can break this.
My simple app with information about this fix: https://github.com/piotr-kedziak/redis-subscribe-stream-puma-fix
Instead of sending a heartbeat to all the clients, it might be easier to just set a watchdog for each connection. [Thanks to #NeilJewers]
class Stream::FixedController < StreamController
def events
# Rails reserve a db connection from connection pool for
# each request, lets put it back into connection pool.
ActiveRecord::Base.clear_active_connections!
redis = Redis.new
watchdog = Doberman::WatchDog.new(:timeout => 20.seconds)
watchdog.start
# Redis (p)subscribe is blocking request so we need do some trick
# to prevent it freeze request forever.
redis.psubscribe("messages:*") do |on|
on.pmessage do |pattern, event, data|
begin
# write to stream - even heartbeat - it's sometimes chance to
response.stream.write("event: #{event}\ndata: #{data}\n\n")
watchdog.ping
rescue Doberman::WatchDog::Timeout => e
raise ClientDisconnected if response.stream.closed?
watchdog.ping
end
end
end
rescue IOError
rescue ClientDisconnected
ensure
response.stream.close
redis.quit
watchdog.stop
end
end
If you can tolerate a small chance of missing a message you can use subscribe_with_timeout:
sse = SSE.new(response.stream)
sse.write("hi", event: "hello")
redis = Redis.new(reconnect_attempts: 0)
loop do
begin
redis.subscribe_with_timeout(5 * 60, 'mycoolchannel') do |on|
on.message do |channel, message|
sse.write(message, event: 'message_posted')
end
end
rescue Redis::TimeoutError
sse.write("ping", event: "ping")
end
end
This code subscribes to a Redis channel, waits for 5 minutes, then closes connection to Redis and subscribes again.
How can I send data to a WebSocket using Ruby in a Background Process?
Background
I already have a separate ruby file running a Websocket server using the websocket-eventmachine-server gem. However, within my Rails application, I want to send data to the websocket in a background task.
Here is my WebSocket server:
EM.run do
trap('TERM') { stop }
trap('INT') { stop }
WebSocket::EventMachine::Server.start(host: options[:host], port: options[:port]) do |ws|
ws.onopen do
puts 'Client connected'
end
ws.onmessage do |msg, type|
ws.send msg, type: type
end
ws.onclose do
puts 'Client disconnected'
end
end
def stop
puts 'Terminating WebSocket Server'
EventMachine.stop
end
end
However, in my background process (I'm using Sidekiq), I'm not sure how to connect to the WebSocket and send data to it.
Here's my Sidekiq worker:
class MyWorker
include Sidekiq::Worker
def perform(command)
100.times do |i|
# Send 'I am on #{i}' to the Websocket
end
end
end
I was hoping to be able to do something like EventMachine::WebSocket.send 'My message!' but I don't see an API for that or something similar. What is the correct way to send data to a WebSocket in Ruby?
Accepted Answer:
Af your keeping your current websocket server:
You can use Iodine as a simple websocket client for testing. It runs background tasks using it's own reactor pattern based code and has a websocket client (I'm biased, I'm the author).
You could do something like this:
require 'iodine/http'
Iodine.protocol = :timers
# force Iodine to start immediately
Iodine.force_start!
options = {}
options[:on_message] = Proc.new {|data| puts data}
100.times do |i|
options[:on_open] = Proc.new {write "I am number #{i}"}
Iodine.run do
Iodine::Http.ws_connect('ws://localhost:3000', options)
end
end
P.S.
I would recommend using a framework, such as Plezi, for your websockets (I'm the author). Some frameworks let you run their code within a Rails/Sinatra app (Plezi does that and I think Faye, although not strictly a framework, does that too).
Using EM directly is quite hardcore and there are a lot of things to manage when dealing with Websockets, which a good framework helps you manage.
EDIT 3:
Iodine WebSocket client connections are (re)supported starting with Iodine 0.7.17, including TLS connections when OpenSSL >= 1.1.0.
The following code is an updated version of the original answer:
require 'iodine'
class MyClient
def on_open connection
connection.subscribe :updates
puts "Connected"
end
def on_message connection, data
puts data
end
def on_close connection
# auto-reconnect after 250ms.
puts "Connection lost, re-connecting in 250ms"
Iodine.run_after(250) { MyClient.connect }
end
def self.connect
Iodine.connect(url: "ws://localhost:3000/path", handler: MyClient.new)
end
end
Iodine.threads = 1
Iodine.defer { MyClient.connect if Iodine.master? }
Thread.new { Iodine.start }
100.times {|i| Iodine.publish :updates, "I am number #{i}" }
EDIT 2:
This answer in now outdated, since Iodine 0.2.x doesn't include a client any longer. Use Iodine 0.1.x or a different gem for websocket clients.
websocket-eventmachine-server is a websockets server.
If you want to connect to a websocket server using ruby, you can do it with some gems, like
https://github.com/igrigorik/em-websocket: Both server and client, also based on eventmachine.
ruby-websocket-client: Client only