基于mqtt的消息推送（二）服务端实现

基于Mosca的服务端实现

Mosca简介，Mosca基于node.js开发，特性引用自项目首页介绍如下：

Features

• MQTT 3.1 and 3.1.1 compliant.
• QoS 0 and QoS 1.
• Various storage options for QoS 1 offline packets, and subscriptions.
• As fast as it is possible.
• Usable inside ANY other Node.js app.
• Supports Node.js v0.10 and v0.12.
• Supports io.js v1.x and v2.x and v3.x (please do not use v3.1.0)

需要特别说明的是Mosca并不支持Qos 2。

为什么选择Mosca？首先基于node.js开发，上手难度相对较小，其次协议支持完整，除了不支持Qos 2，其它的基本都支持。持久化支持redis以及mongo。二次开发接口简单。部署非常简单，并且支持docker镜像。

开发步骤

安装Mosca

本文环境假设你已经安装了node.js环境以及redis，我本机的环境如下：mac ox 10.11.2 node.js v0.12 redis最新版本。

Mosca项目托管地址：https://github.com/mcollina/mosca
官方wiki：https://github.com/mcollina/mosca/wiki

安装非常简单，源引自官方说明如下：

Standalone

1 2	npm install mosca bunyan -g mosca -v | bunyan

Embedded

1	npm install mosca --save

启动脚本

官方给了一个简单的例子，如下是我现在使用的测试代码：

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var mosca = require('mosca') //ascoltatore是Mosca作者开发的一个订阅与发布类库，Mosca核心的订阅与发布模型 var ascoltatore = { type: 'redis', //指定类型，mongo的写法请参考官方wiki redis: require('redis'), db: 1, port: 6379, return_buffers: true, // to handle binary payloads //指定数据保留多长时间，单位毫秒 ttl: { // TTL for subscriptions is 23 hour subscriptions: 23 * 60 * 60 * 1000, // TTL for packets is 23 hour packets: 23 * 60 * 60 * 1000, }, host: "localhost" }; //基本参数设置 var moscaSettings = { port: 1883, //设置监听端口 backend: ascoltatore, maxInflightMessages: 10240, //设置单条消息的最大长度，超出后服务端会返回 //设置WebSocket参数 http: { port: 1884, bundle: true, static: './' }, //数据持久化参数设置 persistence: { factory: mosca.persistence.Redis, db: 1, port: 6379, return_buffers: true, // to handle binary payloads ttl: { // TTL for subscriptions is 23 hour subscriptions: 23 * 60 * 60 * 1000, // TTL for packets is 23 hour packets: 23 * 60 * 60 * 1000, }, host: "localhost" } }; //如果需要用户登录验证权限，需要改写此方法 //这里以简单判断了用户名和密码为例，真实环境可以连接实际业务系统的鉴权服务 var authenticate = function(client, username, password, callback) { var authorized = (username === 'test' && password.toString() === 'passwd'); if (authorized) client.user = username; callback(null, authorized); } function authPub(client, topic, payload, callback) { callback(null, payload); } function authSub(client, topic, callback) { callback(null, topic); } var server = new mosca.Server(moscaSettings); server.on('ready', setup); server.on('clientConnected', function(client) { console.log('client connected', client.id); }); server.on('published', function(packet, client) { console.log('Published', packet.topic + packet.payload); }); // fired when the mqtt server is ready function setup() { server.authenticate = authenticate; server.authorizePublish = authPub; server.authorizeSubscribe = authSub; console.log('Mosca server is up and running') }

二次开发

可以监听的事件列表

• clientConnected : when a client is connected; the client is passed as a
  parameter.
• clientDisconnecting : when a client is being disconnected; the client is
  passed as a parameter.
• clientDisconnected : when a client is disconnected; the client is passed as
  a parameter.
• published : when a new message is published; the packet and the client are
  passed as parameters.
• delivered : when a client has sent back a puback for a published message; the packet and the client are
  passed as parameters.
• subscribed : when a client is subscribed to a topic; the topic and the
  client are passed as parameters.
• unsubscribed : when a client is unsubscribed to a topic; the topic and the
  client are passed as parameters.

有了上面可以监听到事件你就可以根据自己的业务进行相应的开发，拦截特定的事件并添加业务代码

ascoltatore托管地址 https://github.com/mcollina/ascoltatori

高级参数设置可以参考 https://github.com/mcollina/mosca/wiki/Mosca-advanced-usage

权限验证可以参考 https://github.com/mcollina/mosca/wiki/Authentication-&-Authorization

配置ssl可以参考 https://github.com/mcollina/mosca/wiki/TLS-SSL-Configuration

配置WebSocket可以参考 https://github.com/mcollina/mosca/wiki/MQTT-over-Websockets

写在最后

感谢Mosca的作者mcollina，Mosca非常强大，并且足够简单。下篇文章会介绍如何利用IOS和Android开源客户端类库与Mosca对接，敬请期待！

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转载： http://targe.me/2015/12/29/mqtt-second/