Air Quality node sample
There’s a fully working example with uBlox N21x and nRF51 available on GitHub.
DTLS, CoAP over DTLS and FOTA for Raspberry Pi
This shows how to use DTLS in C both with and without CoAP on top. The FOTA sample shows how to do a firmware download. The samples run on a Raspberry Pi but will compile for all frameworks that uses C, mbedTLS, libcoap and plain sockets. All samples are in the following repos on GitHub: