WakaamaNode 
This is a Lightweight M2M library meant to be used for embedded/constrained devices with a convenient C++ API and bindings for C. Get Started.
Lightweight M2M is a protocol from the Open Mobile Alliance for M2M or IoT device management and communication. It is a convention on top of CoAP/UDP which itself is a light and compact protocol with an efficient resource data model. It follows a server/client architecture with Request/Response semantics (GET, POST, PUT, DELETE), as well as observable resources. Optional DTLS (Datagram TLS) ensures secure communication between LwM2M Servers and LwM2M Clients.
The CoAP/lwM2M data model is explained in the documentation.
A lot of common and not so common object and resource identifiers are standardised via the OMA Object & Resource Registry. For example object 3311 is for light controls, 3312 for power sources such as smart plugs.
Features
- The well-tested Eclipse Wakaama provides the underlying lwM2M protocol.
- A powerful Connections API allows to configure lwM2M servers
- lwM2M object definition API for C and C++
- All LwM2M Objects of the OMA Registry are predefined for the C++ Objects API.
- 3 Platform integrations (posix/win32, esp8266-sdk, freertos)
- 2 Network stack integrations (posix/win32, lwIP)
- 2 Firmware update integrations (posix/Win32, arduino OTA)
- Supports optional DTLS via mbedTLS
- All API functionality and library<-->wakaama server communication is covered by tests.
Have a look at the documentation: https://openhab-nodes.github.io/wakaamaNode/
License
- This platform code and API wrappers are provided under the MIT License (MIT).
- Wakaama is provided under the Eclipse Public License - v2.0.
- TinyFSM is provided unter The MIT License (MIT), Copyright (c) 2012-2018 Axel Burri
- Optional-lite, Span-lite, String-View-Lite is provided under the Boost Software License 1.0, Copyright (c) Martin Moene