CoAP is a light-weight IoT protocol for constrained devices. CoAP protocol is UDP based, but similar to HTTP it uses request-response model. CoAP observes option allows to subscribe to resources and receive notifications on resource change.
Controllino Cloud server nodes act as a CoAP Server that supports both regular and observe requests.
You can find CoAP client libraries for different programming languages on the web. Examples in this article will be based on CoAP CLI.
NOTE: CoAP cli does not support query parameters. If you require to use query parameters, you should use CoAP Client instead. To install the coap-client please execute:
Ubuntu 20.04: sudo apt install libcoap2-binUbuntu 18.04: sudo apt install libcoap1-bin
We will use access token device credentials in this article and they will be referred to later as $ACCESS_TOKEN. The application needs to include $ACCESS_TOKEN as a path parameter into each CoAP request. Possible error codes and their reasons are:
4.00 Bad Request - Invalid URL, request parameters or body.4.01 Unauthorized - Invalid $ACCESS_TOKEN.4.04 Not Found - Resource not found.