WebSockets+Redis构建EventMachine

EventMachine 是一个Ruby的事件驱动网络库,本文不是要介绍它,而是要介绍一个以RedisPub/Sub 机制为后端,以WebSockets为前端的类EventMachine实现。

前端代码,创建Socket连接到本地8081端口,当有消息push过来的时候,将消息打印到指定的div里:

<!DOCTYPE html>

<html>
<head>
	<title>Websockets!</title>
	<script>
	function onMessage(evt) {
		con = document.getElementById("console");
		con.innerHTML += evt.data;
		con.innerHTML += '<br />';
	}
	websocket = new WebSocket("ws://localhost:8081");
	websocket.onmessage = function(evt) { onMessage(evt); };
	</script>
</head>

<body>
	<div id="console">
	</div>
</body>
</html>

后端代码:

require 'redis'
require 'em-websocket'

SOCKETS = []
@redis = Redis.new(:host => '127.0.0.1', :post => 6379)

# Creating a thread for the EM event loop
Thread.new do
  EventMachine.run do
    # Creates a websocket listener
    EventMachine::WebSocket.start(:host => '0.0.0.0', :port => 8081) do |ws|
      ws.onopen do
        # When someone connects I want to add that socket to the SOCKETS array that
        # I instantiated above
        puts 'creating socket'
        SOCKETS << ws
      end

      ws.onclose do
        # Upon the close of the connection I remove it from my list of running sockets
        puts 'closing socket'
        SOCKETS.delete ws
      end
    end
  end
end

# Creating a thread for the redis subscribe block
Thread.new do
  @redis.subscribe('ws') do |on|
    # When a message is published to 'ws'
    on.message do |chan, msg|
     puts "sending message: #{msg}"
     # Send out the message on each open socket
     SOCKETS.each {|s| s.send msg}
    end
  end
end

sleep

开启8081端口接受连接,同时连到Redis上订阅ws这个key的消息

当前后端都启动并连接上后,你就可以用如下代码往Redis的ws这个key上写消息,页面上就能看到push过来的消息了:

require 'redis'
@redis = Redis.new(:host => '127.0.0.1', :post => 6379)
@redis.publish 'ws', 'Something witty'

来源:jessedearing.com
have fun!

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