Leshan

Leshan#

Build and Run#

The Leshan server can also run locally, without the need of a docker container.

host:~$ sudo apt update
host:~$ sudo apt install openjdk-17-jdk maven
host:~$ source venv/bin/activate
host:~$ cd workspace/flownexus/server/leshan
host:~/workspace/flownexus/server/leshan$ ./leshan_build_run.sh

The Leshan server should now be up and running under the following URL: http://localhost:8080.

Leshans Role in flownexus#

Lehsan is considered a production ready LwM2M server and is used in many commercial products. It is used as an LwM2M server in flownexus. It is responsible for registering and managing endpoint. There is no application specific logic implemented in Leshan related Java code within flownexus. The goal is to have all application logic within the Django application.

Leshan can be seen as a proxy between the LwM2M endpoints Django. There is no direct communication between Django and endpoints.

LwM2M Observe#

LwM2M observe#

The LwM2M observe operation allows an LwM2M Server to monitor changes to specific Resources, Resources within an Object Instance, or all Object Instances of an Object on an LwM2M Client. An endpoint must remember these observation requests until re-registration.

Single and CompositeObserve#

Leshan supports two types of observe requests: Single and CompositeObserve. SingleObserve is a simple observe request for a single resource. CompositeObserve is a more complex observe request that subscribes to multiple Resources of one Object.

Once an endpoint registers to Leshan, Leshan will initiate an observe request to selected resources. With every new registration of an endpoint, the observe requests are re-initiated.

Note

The observe initiation will move from Leshan to Django with future versions. Django is informed about new registrations and will then initiate the observe requests. This allows a more centralized approach and better control over the observe requests via the database model.

For testing, the Leshan server currently initiates the following two observe requests:

  • SingleObserve (Temperature Sensor Value): {3303, 0, 5700}

  • CompositeObject (Custom Object Id): {10300}