This directory contains examples showing basic usage such as ping, discover, put/post etc. and raw request handling using the coap.me and californium test servers.
A reasonable starting point is the get_resource.dart example.
The coap.me API: https://coap.me/crawl/coap://coap.me:5683
The californium plugtest API is exercised in their plugtests: https://github.com/eclipse/californium/blob/master/demo-apps/cf-plugtest-client/src/main/java/org/eclipse/californium/plugtests/PlugtestClient.java