EM.run do

  WebSocket::EventMachine::Server.start(:host => "0.0.0.0", :port => 8080) do |ws|
    ws.onopen do
      puts "Client connected"
    end

    ws.onmessage do |msg, type|
      puts "Received message: #{msg}"
      ws.send msg, :type => type
    end

    ws.onclose do
      puts "Client disconnected"
    end
  end

end

EM.run do

  ws = WebSocket::EventMachine::Client.connect(:uri => 'ws://localhost:8080')

  ws.onopen do
    puts "Connected"
  end

  ws.onmessage do |msg, type|
    puts "Received message: #{msg}"
  end

  ws.onclose do |code, reason|
    puts "Disconnected with status code: #{code}"
  end

  EventMachine.next_tick do
    ws.send "Hello Server!"
  end

end

jruby server.rb
jruby client.rb

Disconnected with status code: 1002