Research And Implementation Of Coap Reliable Group Communication

Internet of Things is an extension and expansion of network, which realizes M2M(machine to machine) information exchanges. Because of many devices in IoT are resource-limited, the traditional HTTP is too large and heavy-weight to apply in IoT. To cope with the restrictions,IETF(Internet Enginnering Task Force) Core(Constrained RESTful Environment) working group designed a RESTful protocol called CoAP(Constrained of Application Protocol). CoAP is synonymous with restricted the application of the agreement, which is applied in the constrained devices and constrained network as and application layer network protocol. Constrained network has two features, one is the large number, another is the functional and regional relevance, which makes group communication becomes an important way of communication. The current CoAP can only implements unreliable group communication based on IP multicasting. The unreliable CoAP group communication is not satisfied for lightweight M2M application requirements and architecture documents proposed by OMA. In the application scenarios proposed by OMA, unreliable CoAP group communication will bring a great deal of risk.In order to solve the problems brought by the unreliable of CoAP group communication, this paper proposes a novel approach which is based on proxy to make the CoAP group communication reliable. On the basis of the scheme, the author uses java based on the Californium (cf)CoAP framework to realize the reliable group communication. The mechanism realized choosing the way of retransmission according to the percentage of nodes, and realized the control of sleep nodes.Finally, the autor conducted an experiment using the mechanism mentioned above to verify the function of its integrity. And on the basis,the article conducted experiments using reliable group communication based on proxy mechanism and unicast-based mechanism respectively,and then compared the experiments results. The experiment result proves the mechanism based on proxy is a feasible implementation scheme, and has better performance compared to the unicast-based mechanism.