# LWM2M

{% hint style="info" %}
LWM2M is currently in a preview only mode for Enterprise. Please contact us to get a demo. 
{% endhint %}

[Lightweight Machine to Machine](https://www.omaspecworks.org/what-is-oma-specworks/iot/lightweight-m2m-lwm2m/) specification is based on CoAP and is developed by the [Open Mobile Alliance](https://openmobilealliance.org/) for the Internet of Things. The advantage of LWM2M over others is that it runs on UDP/DTLS and could even use SMS in some constrained cases. The underlying protocol for LWM2M is the [Constrained Application Protocol](https://tools.ietf.org/html/rfc7252) (CoAP). 

![](https://1549501356-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LhKFvCh4dnxgthNTIuu%2F-M8PgUVlmBFlPVvo_0UG%2F-M8PjeMZ4nTuXlWxtZJI%2Fimage.png?alt=media\&token=bf32aa6b-ac04-4172-b57d-be85df3ec839)

Currently the LWM2M client settings are minimalist. The client will automatically try to register to the provided server. In order to use the LWM2M client, you must build a smartobject in your state variable in device initialization. An example of a LWM2M device initialization code is 

```
{
  state.temp = 20;
  state.led = false;
  
  state.so = new smartObject(); 
  state.so.init('temperature', 0, 
    {
        _state : state,
        sensorValue: {
        read: function (cb) {
            console.log('Read called for Sensor'); 
            cb(null,state.temp); },
        write: function (value, cb){ 
            console.log('Write called for Sensor with value', value)
            cb(null,state.temp); 
        }},
        units: 'C'	
    }); 


    // led
  state.so.init('lightCtrl', 0 , {
        _state: state,
        onOff: {
            read: function (cb) {
                cb(null, state.led);
            },
            write: function (val, cb) {
                state.led = val;
                cb(null, state.led);
            }
        }
    });


  //no need for return 
}

```

Above Function will initiate two resource objects for your device. The server could read/write and observe to these resources and the handlers will be invoked. 

The message sending functions are also a little different in case of LWM2M

```
{
    state.temp = 25+index();
    
    /* Update using a trigger method
    state.so.write('temperature', 0, 'sensorValue', state.temp , function (err, data) {
        if (err) {
            console.log(err);   // Error: 'Resource is unwritable.'
            console.log(data);  // _unwritable_
        }
    });
    */
    
    
    // Read using trigger method
    /*
    state.so.dump('temperature', 0, function (err, data) {
        console.log(data);
        
    })
    */
    
	var payload = {
        pathname: '/.well-known/core',
        payload: '</>;hb,</1/0>;obs,</3/0>;obs,</4/0>;obs,</3303/0>;obs', 
        method: 'GET', 
        waitResponse: false,
        options: { 
            'Content-Format': 'application/link-format' 
        },
        query: '' 
	}
	
    return JSON.stringify(payload);
}
```

A JSON object must be returned in stringified form, indicating the next action to be performed.&#x20;