https://github.com/mohdrashid/resmetry

Request-response operation over MQTT protocol
https://github.com/mohdrashid/resmetry

callback mqtt mqtt-client mqtt-protocol nodejs request response topic

Last synced: 20 days ago
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Request-response operation over MQTT protocol

• Host: GitHub
• URL: https://github.com/mohdrashid/resmetry
• Owner: mohdrashid
• License: mit
• Created: 2017-01-01T09:10:59.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2017-06-28T09:49:21.000Z (over 7 years ago)
• Last Synced: 2024-10-03T08:05:15.680Z (about 1 month ago)
• Topics: callback, mqtt, mqtt-client, mqtt-protocol, nodejs, request, response, topic
• Language: JavaScript
• Homepage: https://droidhat.com/mqtt-based-request-response-messaging
• Size: 670 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

Awesome Lists containing this project

README

        
Resmetry is a client library for the [MQTT](http://mqtt.org/) protocol, written

in JavaScript for node.js with the aim of building request-response communication on top of mqtt protocol. 

Resmetry supports both on request connection and always-on connection.

This library relies on [MQTT.js library](https://www.npmjs.com/package/mqtt) for interacting with mqtt server.



## Installation

```sh

npm install resmetry --save

```



## Example

```js

var resmetrylib=require('resmetry');

var host='mqtt://localhost';

//Standard settings available in npm package mqtt

var settings={

  protocolId: 'MQIsdp',

  protocolVersion: 3

};

/**

 * The last parameter should be true for an always active connection, false for a one time connection

 * @type {resmetry}

 */

var resmetry= new resmetrylib(host,settings,false);

/*

* Get mqtt client for advanced operations, Refer npm package mqtt for more information

* For other features offered by MQTT, the modifications can be made using the object

* Only applicable true is passed the last parameter of the constructor

*/

//var mqtt=resmetry.getMQTTClient();

//MQTT operations

//mqtt.subscribe('request/1');

//Connection listener

resmetry.on('connect',function(message){

  console.log(message);

});

//Message event listener

var temp=25;

resmetry.on('message',function(topic,message){

  console.log("Topic: "+topic,"Message: "+message);

  if(topic==='request/1'&&message==='temp'){

    mqtt.publish('response/1',temp+'',{qos:2});

  }

});

//Making a request to topic 'request' with message 'send me details' whose expected result goes to topic response with options

var options={qos:2};

//Options are standard options available for publishing in npm package mqtt

resmetry.request('request/1','temp',options,'response/1',function(err,response){

  console.log('Response:'+response);

});

```

output:

```

Connected

Topic: request/1 Message: temp

Topic: response/1 Message: 25

Response:25

```



## API

  * new resmetry()

  * resmetry.request()

  * resmetry.getMQTTClient()

  * resmetry.disconnect()

-------------------------------------------------------



### new resmetry(host,settings,connectionType)

Connects to the broker specified by the given url and options and

ted options. Options are as mentioned in connect part of npm package [mqtt.js](https://www.npmjs.com/package/mqtt#connect)

ConnectionType specifies whether current operation is one-time or continuous. One-time activated by passing false, makes the connection end after obtaining the response.

Whereas, continuous operation mode activated by passing true, runs forever.

-------------------------------------------------------



### resmetry.request(topic,data,options,responseTopic,callback)

* 'topic' is the topic to which message will be send to.[Like request]

* 'data' is the message which needs to be passed along with request

* 'options' are additional options like qos and retain features. Refer npm package [mqtt.js publish](https://www.npmjs.com/package/mqtt#publish)

* 'responseTopic' is the the topic to which response will be send to[Like response]

* 'callback' is where any err or result will be passed

-------------------------------------------------------



### resmetry.getMQTTClient()

Returns the mqtt client for the functionality of add your listeners other than 'message' event.Refer [mqtt.js Events](https://www.npmjs.com/package/mqtt#connect) for information on events and other functionalities.

-------------------------------------------------------



### resmetry.disconnect()

Disconnects the active MQTT client connection

-------------------------------------------------------



## Events

  * connect

  * message

  * error

  -------------------------------------------------------

  

  ### resmetry.on('connect',function(message))

  * Fired when mqtt client connects to server

  * 'message' is a string saying Connected

  -------------------------------------------------------

  

  ### resmetry.on('message',function(topic,message))

  * Fired when a message comes

  * 'topic' is the topic to which message was published

  * 'message' contains the message send in the topic

  

  -------------------------------------------------------

  

  ### resmetry.on('error',function(error))

  * Fired when error is encountered

  * error contains details related to the error thrown

-------------------------------------------------------



## License

MIT