In the IoT (Internet of Things) domain, it is still a challenge to modify the routing behavior of IoT traffic at the decentralized backbone network. In this paper, centralized and flexible software-defined networking (SDN) is utilized to route the IoT traffic. The management of IoT data transmission through the SDN core network gives the chance to choose the path with the lowest delay, minimum packet loss, or hops. Therefore, fault-tolerant delay awareness routing is proposed for the emulated SDN-based backbone network to handle delay-sensitive IoT traffic. Besides, the hybrid form of GNS3 and Mininet-WiFi emulation is introduced to collaborate the SDN-based backbone network in GNS3 and the 6LoWPAN (IPv6 over Low Power Personal Area Network) sensor network in Mininet-WiFi.