jennyChat-ws

Barebone chat program using WebSocket. Testable in CLI.

This project uses faye-websocket gem for WebSocket implementation.

WebSocket

Constructing a WebSocket request is essentially an HTTP connection that includes a request to upgrade the connection to use WebSocket. WebSockets is built on TCP sockets - the WebSocket API re-assembles the TCP chunks of data into frames which are assembled into messages before invoking the message event handler once per message.

Server Side

This program uses thin as server and fires the lambda block with thin.run. faye-websocket provides an adapter to enable upgrading the handshake to websocket using thin.

require 'faye-websocket'
require 'rack'

Faye::WebSocket.load_adapter('thin')

# use thin.run(wsServer,...) to run the lambda and get env
    thin = Rack::Handler.get('thin')
    thin.run(@wsServer, :Host => @socket_host, :Port => @socket_port)

The lambda block for initializing the WebSocket server:

wsServer = lambda do |env|
      if Faye::WebSocket.websocket?(env)
        # It is a WebSocket connection
        ws = Faye::WebSocket.new(env)


        # .......


        # Return async Rack response
        ws.rack_response
      else
        # Normal HTTP request
        [200, { 'Content-Type' => 'text/plain' }, ['Hello, this is a normal HTTP Request.']]
      end
    end

Then simply use the available apis from faye-websocket: on :open,on :message and on :close.

Client side

Use EventMachine to run (multiple) clients. Start the EM reactor by using EM.run.

require 'faye/websocket'
require 'eventmachine'

EM.run do
  ws = Faye::WebSocket::Client.new("ws://localhost:4567/")

  # ....

end

Within the EM run block, add all the websocket handlers on :open,on :message and on :close. Note that to be able to test in CLI with user input message, use new thread for command line input loop (looping so user can input multiple times) - so that waiting for user input won't block other on :message handler making messages being delayed.

ws.on :message do |event|
  puts event.data
  Thread.new {
    loop {
        msg = $stdin.gets.chomp
        ws.send(msg)
      }
  }
end

Stop the EM loop by EM.stopwhen the connection closes to gracefully exit the program.

ws.on :close do |event|
  ws.nil
  puts "Connection cannot be established. Exiting..."
  EM.stop
end