LwM2M Driver

dc3-driver-lwm2m connects LwM2M devices to IoT DC3——it embeds a LwM2M server, accepts device registrations, and reads/writes resources on a device by the three-part Object / Object Instance / Resource path.

LwM2M (Lightweight M2M) is an OMA-defined protocol for IoT device management and data collection. It runs over CoAP (default UDP 5683, DTLS/CoAPS 5684 for encryption). It abstracts a device's capabilities into an "object tree": each Object (e.g. 3303=Temperature) contains one or more Object Instances (multiple instances of the same resource type), and each instance contains one or more Resources (e.g. 5700=Sensor Value). Accessing a specific value means giving the path /<objectId>/<objectInstanceId>/<resourceId>. It is common on battery-powered, remotely deployed endpoints (NB-IoT modules, smart meters, environmental sensors—anywhere remote management and low power consumption are both needed).

Unlike drivers such as Modbus or CoAP that actively connect to devices, this driver embeds a LwM2M server based on Eclipse Leshan: the device acts as a LwM2M client and registers to this server using its own endpoint name; once registered, the driver issues reads/writes to that endpoint by the path configured on each point.

• Driver name / code: LwM2M Driver / Lwm2mDriver
• Type: DRIVER_CLIENT

Currently a skeleton implementation (WIP)

This driver is currently a skeleton; protocol-level I/O is not yet fully implemented (the class doc of Lwm2mDriverCustomServiceImpl explicitly marks it a "work-in-progress skeleton"). Treat it as an onboarding template / starting point, not a production-ready driver.

Driver Configuration (device-level driver-attribute)

When onboarding a LwM2M device, fill in these attributes on the device:

Attribute	code	Type	Default	Remark
Endpoint	endpoint	STRING	(empty)	LwM2M device endpoint name
Server Host	serverHost	STRING	0.0.0.0	LwM2M server bind address
Server Port	serverPort	INT	5683	CoAP port
Secure Port	securePort	INT	5684	CoAPS/DTLS port
Security Mode	securityMode	STRING	NOSEC	Security mode: NOSEC, PSK
PSK Identity	pskIdentity	STRING	(empty)	PSK identity (when securityMode=PSK)
PSK Key	pskKey	STRING	(empty)	PSK key in HEX (when securityMode=PSK)

Here endpoint is the key that maps this device to a registered LwM2M client—it must match the endpoint name the device reports at registration exactly. serverHost / serverPort / securePort determine which address and ports the embedded server listens on.

Point Configuration (point-attribute)

Fill in one LwM2M resource path on each point:

Attribute	code	Type	Default	Remark
Object ID	objectId	INT	0	LwM2M Object ID (e.g. 3303=Temperature)
Object Instance ID	objectInstanceId	INT	0	LwM2M Object Instance ID
Resource ID	resourceId	INT	0	LwM2M Resource ID (e.g. 5700=Sensor Value)
Observe	observe	STRING	false	Enable LwM2M Observe: true, false

The three-part path decides which resource to read

The driver assembles objectId / objectInstanceId / resourceId into the path /<objectId>/<objectInstanceId>/<resourceId>, issues a read to the device endpoint, and the returned value is the point value for that point. The point's data type (Point's pointTypeFlag) must match the actual data type of that Resource. observe=true enables LwM2M Observe (subscription-style reporting) on the resource, so the device pushes proactively on value change rather than being polled each round.

LwM2M has no separate command-attribute table (command-attribute: [ ] is empty in the yml)—the write target of a writable point is simply the point's own /<objectId>/<objectInstanceId>/<resourceId> path. When a write command is issued, the driver writes directly to that path, with no extra command attributes needed.

Collection and Health

• Collection cycle: default cron 0/30 * * * * ? (reads every 30 seconds, issuing one read to each point's resource path).
• Custom job: the driver ships a built-in custom schedule, default cron 0/5 * * * * ? (every 5 seconds), for the driver's own periodic logic, independent of point collection.
• Health / liveness: device health check default cron 0/15 * * * * ?, lease timeout 45 seconds. Whether a device is online depends on whether its endpoint is still registered on the embedded server—see device for the liveness mechanism.

Minimal Onboarding Example

Onboard a LwM2M sensor whose endpoint name is urn:imei:860000000000001 and whose temperature resource is at /3303/0/5700:

1. Create a device with LwM2M Driver, and set the driver attributes endpoint=urn:imei:860000000000001, serverHost=0.0.0.0, serverPort=5683, securityMode=NOSEC (plaintext mode needs no PSK).
2. Have the LwM2M client register to this service's port 5683 using the same endpoint name.
3. Add a temperature point (READ_ONLY) to the profile bound to the device, with point attributes objectId=3303, objectInstanceId=0, resourceId=5700.
4. Start the driver. Once the device registers successfully, within 30 seconds you will see the temperature value read back in the point value.

Common Pitfalls

The endpoint name must match the device's registration exactly

Device liveness is judged by matching the endpoint name on the embedded server. If the endpoint the device actually registers with (commonly urn:imei:<IMEI> or a vendor-defined string) and the endpoint filled on the device differ by even one character, they will not match: the device stays offline and reads return nothing. Before onboarding, confirm exactly what endpoint name the device firmware uses to register.

With PSK enabled, configure Identity and Key as a pair, and use port 5684

When securityMode=PSK, the encrypted handshake (DTLS) goes over securePort (default 5684), and pskIdentity and pskKey must match what is provisioned on the device side, with pskKey being a HEX string. If any of the three does not match, the DTLS handshake fails and the device cannot register. To just get the link working first, securityMode=NOSEC over the plaintext 5683 port is the simplest.

Further Reading

• Driver — the general driver model and registration mechanism
• Attributes and Config — the three layers behind attributes like endpoint / objectId
• Device Onboarding — a complete onboarding walkthrough
• CoAP Driver — the CoAP protocol driver that LwM2M builds upon