Two of the most promising IoT protocols for small devices are MQTT and CoAP. Here is the description and comparison of MQTT and CoAP. See the link of MQTT and CoAP, IoT Protocols.
Here is the some useful open source projects to implement MQTT and CoAP. You may compile the applications and libraries with the specific tool chain and deploy them in IOx of C819, CGR1120/1240, and IR829/809.
1. MQTT (formerly MQ Telemetry Transport):
The very popular mosquitto broker recently moved under the Eclipse umbrella too – the Eclipse Mosquitto project contains both mosquitto, and a fully open-sourced Really Small Message Broker from IBM, which also happens to support MQTT-SN.
2. CoAP (Constrained Applications Protocol):
libcoap is an open source C implementation that focuses on decoding and encoding, leaving the actual protocol to the application. And both of coap-client and coap-server are provided as an example.
CoAPthon is a python library for the CoAP protocol compliant with the RFC, with a branch available that uses the Twisted framework.
Californium is a powerful CoAP framework targetting back-end services and stronger Internet of Things devices. It is an open source Java implementation, and provides a convenient API for RESTful Web services that support all of CoAP's features.
You may refer to CoAP Implementation for more details.