The last few years have witnessed exponential rise in internet-of-things (IoT) systems for communication; yet, ensuring quality-of-service (QoS) and transmission reliability over mobile topology has remained challenge. Despite the fact that the use of software defined networks (SDN) have enabled IoTs to achieve resource efficiency and reliability; it doesn’t guarantee optimality of the solution over the network with high dynamism and non-linearity. Moreover, the major at hand SDN-IoT protocols have applied standalone node parameters to perform routing and allied transmission decision that confine its robustness over dynamic network topologies. Interestingly, none of the state-of-art SDN-IoT protocols could address the problem of iterative link-outage and corresponding network discovery cost. Furthermore, even multi-path selection strategies too failed in addressing the problem of joined shortest path selection and allied iterative link-outage due to the common node failure. Considering it as motivation, in this paper a novel and robust Heuristic-Driven Disjoint Alternate Path Switching -based Fault-Resilient Multi-Constraints Routing Protocol for SDN-mIOT system (HDAP-SDNIoT) is proposed. HDAP-SDNIoT exploits multiple dynamic parameters like medium access control information, flooding and congestion probability information. HDAP-SDNIoT exploits aforesaid node parameters to perform node profiling that serves multi-constraints best forwarding path selection. The proposed model retrieves multiple best alternating paths which are fed as input to the Adaptive Genetic Algorithm (AGA) that retains three disjoint best forwarding paths. HDAP-SDNIoT protocol at first avoids any malicious node(s) to become forwarding node, while it provides auto-switching capability to the forwarding node to select a disjoint forwarding alternate path in case of any link-outage in current forwarding path. _Simulation results confirm robustness of the proposed model in terms of high packet delivery rate of 96.5%, low packet loss rate 3.5% and low delay of 211 ms that affirms its suitability towards real-time SDN-mIoT applications.