1. 安装 websocket 命令行客户端：
   • npm install -g wscat
2. 连接服务器（可通过 cookies.signed 和 request.authorization 进行认证）：
   • wscat -c wss://echo.g-secret.com/cable -H 'Authorization:Token token=8A5A93D8-55EC-429E-9C66-B76CC74F23E5'
3. 订阅频道：
   • 发送：{"command":"subscribe","identifier":"{\"channel\":\"NotificationsChannel\"}"}
   • 返回：
     • {"identifier":"{\"channel\":\"NotificationsChannel\"}","type":"confirm_subscription"}
     • {"identifier":"{\"channel\":\"NotificationsChannel\"}","message":{"message":"当前连接数: 1"}}
4. 发送消息：
   • 发送：{"command":"message","identifier":"{\"channel\":\"NotificationsChannel\"}","data":"{\"message\":\"你好~~\",\"action\":\"speak\"}"}
     • 返回： {"identifier":"{\"channel\":\"NotificationsChannel\"}","message":{"message":"你好~~","action":"speak"}}
   • 发送：{"command":"message","identifier":"{\"channel\":\"NotificationsChannel\"}","data":"{\"action\":\"count\"}"}
     • 返回：{"identifier":"{\"channel\":\"NotificationsChannel\"}","message":{"message":"当前连接数: 1"}}
5. 退订：
   • 发送：{"command":"unsubscribe","identifier":"{\"channel\":\"NotificationsChannel\"}"}
     • 什么也不会返回

# -*- encoding: utf-8 -*-

class NotificationsChannel < ApplicationCable::Channel
  def subscribed
    stop_all_streams
    stream_from channel_id
    count
  end

  def unsubscribed
    stop_all_streams
  end

  def speak(data)
    ActionCableWorker.perform_async(channel_id, data)
  end

  def count
    speak( message: "当前连接数: #{ActionCable.server.connections.count}" )
  end

  private
    def channel_id
      "notifications:#{self.user_id || 'public'}"
    end
end