The research on the Internet of Things (IoT) has made rapid strides towards the definition of a global network of interconnected objects. Some IETF Working Groups are giving major contributions in this direction by standardizing an IPv6based framework for resource-constrained nodes. Although this solution handles different constrained networks' devices, it does not explicitly manage the integration with a key IoT enabler: the RFID (Radio Frequency Identification) technology. In this paper, we propose a CoAP-compliant solution where RFID tags are directly accessible via a reader that acts as a proxy. The RFID tags, behaving as virtual CoAP servers, are included in the IoT realm. Key design aspects are addressed such as tag addressing, service and resource discovery, and mapping of CoAP methods onto RFID commands. Finally, the performance of the proposed solution is evaluated in order to provide useful indications for future deployments.