Privacy and security are the key issues in Industrial Wireless Sensor Networks (IWSN) as the wireless sensor nodes are typically deployed in a hostile environment (i.e., in a remote location where minimum or no human intervention is required) and can be easily compromised by an attacker. Several protocols have been proposed to address these issues. However, none of them can fulfill the required privacy and security goals. Additionally, the traditional network architecture presents a performance bottleneck due to the rapidly increasing traffic volume and heterogeneous sensor nodes. Hence, the existing architecture needs to be upgraded accordingly. In this article, we propose a Software-Defined Networking (SDN)-based authentication protocol for real-time data transfer in IWSN, called SDIWSN. SDIWSN puts the management and control functions of the network into a set of logically centralized SDN controllers, thus providing a global view of the network. SDIWSN achieves several privacy and security requirements such as anonymity, unlinkability, mutual authentication, key agreement, forward secrecy and robustness against passive and active attacks. Moreover, SDIWSN provides a simple velocity-based strategy to detect cloning attacks. We validate the privacy and security features of SDIWSN using formal and informal verification. Finally, the efficiency of SDIWSN is measured through a performance-based comparison.