C-Implementation of CoAP
libcoap implements a lightweight application-protocol for devices that are constrained their resources such as computing power, RF range, memory, bandwith, or network packet sizes.
libcoap is designed to run on embedded devices as well as high-end computer systems with POSIX OS. Thus, you can develop and test your CoAP applications on your laptop and then move it to your target platform easily.
libcoap has successfully participated in several ETSI IoT CoAP plugtests and is in daily use by various IOT projects in industry and academia. Tools to test against can also be found at coap.technology.