This is the documentation for the latest (master) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down menu on the left and select the desired version.

LwM2M client


Lightweight Machine to Machine (LwM2M) is an application layer protocol based on CoAP/UDP, and is designed to expose various resources for reading, writing and executing via an LwM2M server in a very lightweight environment.

This LwM2M client sample application for Zephyr implements the LwM2M library and establishes a connection to an LwM2M server using the Open Mobile Alliance Lightweight Machine to Machine Technical Specification (Section 5.3: Client Registration Interface).

The source code for this sample application can be found at: samples/net/lwm2m_client.


Building and Running

There are configuration files for various setups in the samples/net/lwm2m_client directory:

  • prj.conf This is the standard default config.

  • overlay-dtls.conf This overlay config can be added for DTLS support via MBEDTLS.

  • overlay-bt.conf This overlay config can be added to enable Bluetooth networking support.

  • overlay-queue.conf This overlay config can be added to enable LWM2M Queue Mode support.

Build the lwm2m-client sample application like this:

west build -b <board to use> samples/net/lwm2m_client -- -DCONF_FILE=<config file to use>

The easiest way to setup this sample application is to build and run it via QEMU using the default configuration prj.conf. This requires a small amount of setup described in Networking with QEMU.

Download and run the latest build of the Leshan Demo Server:

$ wget
$ java -jar ./leshan-server-demo.jar -wp 8080

You can now open a web browser to: http://localhost:8080 This is where you can watch and manage connected LwM2M devices.

Build the lwm2m-client sample application for QEMU like this:

west build -b qemu_x86 samples/net/lwm2m_client
west build -t run

The sample will start and automatically connect to the Leshan Demo Server with an IPv6 client endpoint “qemu_x86”.

To change the sample to use IPv4, disable IPv6 by changing these two configurations in prj.conf:


DTLS Support

To build the lwm2m-client sample for QEMU with DTLS support do the following:

west build -b qemu_x86 samples/net/lwm2m_client -- -DCONF_FILE="prj.conf overlay-dtls.conf"
west build -t run

Setup DTLS security in Leshan Demo Server:

  • Open up the Leshan Demo Server web UI

  • Click on “Security”

  • Click on “Add new client security configuration”

  • Enter the following data:

    Client endpoint: qemu_x86 Security mode: Pre-Shared Key Identity: Client_identity Key: 000102030405060708090a0b0c0d0e0f

  • Start the Zephyr sample

Bluetooth Support

To build the lwm2m-client sample for hardware requiring Bluetooth for networking (IPSP node connected via 6lowpan) do the following:

west build -b <board to use> samples/net/lwm2m_client -- -DCONF_FILE="prj.conf overlay-bt.conf"

The overlay-*.conf files can also be combined. For example, you could build a DTLS-enabled LwM2M client sample for BLENano2 hardware by using the following commands (requires Bluetooth for networking):

west build -b nrf52_blenano2 samples/net/lwm2m_client -- -DCONF_FILE="prj.conf overlay-bt.conf overlay-dtls.conf"

Queue Mode Support

To build the lwm2m-client sample with LWM2M Queue Mode support do the following:

west build -b <board to use> samples/net/lwm2m_client -- -DCONF_FILE="prj.conf overlay-queue.conf"

With Queue Mode enabled, the LWM2M client will register with “UDP with Queue Mode” binding. The LWM2M engine will notify the application with LWM2M_RD_CLIENT_EVENT_QUEUE_MODE_RX_OFF event when the RX window is closed so it can e. g. turn the radio off. The next RX window will be open with consecutive LWM2M_RD_CLIENT_EVENT_REG_UPDATE_COMPLETE event.

WNC-M14A2A LTE-M Modem Support

To build the lwm2m-client sample for use with the WNC-M14A2A LTE-M modem shield do the following:

west build -b <board to use> samples/net/lwm2m_client -- -DCONF_FILE="prj.conf overlay-wncm14a2a.conf"

Sample output without DTLS enabled

The following is sample output from the QEMU console. First, LwM2M engine is initialized. Then, several LwM2M Smart Objects register themselves with the engine. The sample app then sets some client values so that they can be seen in the Leshan Demo Server interface, and finally, the registration request is sent to the server where the endpoint is initialized.

To exit from QEMU enter: 'CTRL+a, x'
[QEMU] CPU: qemu32,+nx,+pae
qemu-system-i386: warning: Unknown firmware file in legacy mode: genroms/multiboot.bin

shell> [lib/lwm2m_engine] [DBG] lwm2m_engine_init: LWM2M engine thread started
[lwm2m_obj_security] [DBG] security_create: Create LWM2M security instance: 0
[lwm2m_obj_server] [DBG] server_create: Create LWM2M server instance: 0
[lwm2m_obj_device] [DBG] device_create: Create LWM2M device instance: 0
[lwm2m_obj_firmware] [DBG] firmware_create: Create LWM2M firmware instance: 0
[lwm2m-client] [INF] main: Run LWM2M client
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/0, value:0x0001c99e, len:6
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/1, value:0x0001c9ab, len:23
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/2, value:0x0001c9c9, len:9
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/3, value:0x0001c9d9, len:3
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/9, value:0x0041a3a4, len:1
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/10, value:0x0041a3b4, len:4
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/17, value:0x0001c9fc, len:16
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/18, value:0x0001ca14, len:5
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/20, value:0x0041a3a4, len:1
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3/0/21, value:0x0041a3b4, len:4
[lib/lwm2m_engine] [DBG] lwm2m_engine_create_obj_inst: path:3303/0
[ipso_temp_sensor] [DBG] temp_sensor_create: Create IPSO Temperature Sensor instance: 0
[lib/lwm2m_engine] [DBG] lwm2m_engine_set: path:3303/0/5700, value:0x0041a3b8, len:8
[lib/lwm2m_rd_client] [INF] lwm2m_rd_client_start: LWM2M Client: qemu_x86
[lib/lwm2m_rd_client] [INF] sm_do_init: RD Client started with endpoint 'qemu_x86' and client lifetime 0
[lib/lwm2m_rd_client] [DBG] sm_send_registration: registration sent [2001:db8::2]
[lib/lwm2m_engine] [DBG] lwm2m_udp_receive: checking for reply from [2001:db8::2]
[lib/lwm2m_rd_client] [DBG] do_registration_reply_cb: Registration callback (code:2.1)
[lwm2m-client] [DBG] rd_client_event: Registration complete
[lib/lwm2m_rd_client] [INF] do_registration_reply_cb: Registration Done (EP='EZd501ZF26')
[lib/lwm2m_engine] [DBG] lwm2m_udp_receive: reply 0x004001ec handled and removed