LWM2M Protocol¶
Lightweight M2M (LWM2M) is a set of protocols defined by the Open Mobile Alliance (OMA) for machine-to-machine (M2M) or Internet of Things (IoT) device management and communications. It can be found here .
LWM2M is based on coap protocol, and can be carried on UDP or SMS.
There are two types of servers:
- LWM2M BOOTSTRAP SERVER. emq-lwm2m does not support such kind of server.
- LWM2M SERVER. emq-lwm2m implements most features of this server type, except for SMS binding.
LWM2M defines service on a device as Object and Resource, which is represented in a XML file. A list of registered XML Objects can be found here .
EMQ-LWM2M plugin¶
EMQ-LWM2M is an EMQ plugin，which implemnts most LWM2M features. MQTT client is able to access LWM2M device through emq-lwm2m plugin, by sending a command and reading its response.
Convert between MQTT and LWM2M¶
Commands from mqtt client to LWM2M device is carried in following topic:
And mqtt payload will be a json format data which specifies the command. Please refer to emq-lwm2m document for details.
Response from LWM2M device to mqtt client is carried in following topic:
And mqtt payload will be a json format data which specifies the command. Please refer to emq-lwm2m document for details.
Parameters¶
File: etc/emq_lwm2m.conf:
lwm2m.port = 5783
lwm2m.certfile = etc/certs/cert.pem
lwm2m.keyfile = etc/certs/key.pem
lwm2m.xml_dir = etc/lwm2m_xml
| lwm2m.port | LWM2M udp port. Port 5783 is used to prevent conflict against emq-coap | |
| lwm2m.certfile | DTLS certificate | |
| lwm2m.keyfile | DTLS private key | ||
| lwm2m.xml_dir | A directory to store XML files which define LWM2M Objects | ||