The use of web services for sensor networking applications is seen as an important part in emerging M2M communications. The Constrained Application Protocol (CoAP) is proposed by the Internet Engineering Task Force (IETF) to optimize the use of the RESTful web service architecture for constrained nodes and networks, for example Wireless Sensor Networks (WSN). In this paper, we present a performance evaluation of the CoAP protocol implemented for the embedded operating system TinyOS. The CoapBlip implementation has been deployed on 20 TelosB motes forming a multi- hop network using the Routing Protocol for Low- power and Lossy Networks (RPL) with the two objective function of MRHOF and OF0. The performance of CoAP has been studied using both objective functions in the routing layer together with having LPL (Low Power Listening) enabled or disabled.