Internet of Things (IoT) is the advanced technology, were the constrained nodes/things (all the objects around us such as chair, home, car, keys, etc.) will be connected to the internet to form a network, for sharing and monitoring the data, remotely. RPL (IPv6 Routing Protocol for Low Power and Lossy networks) is a routing protocol particularly designed for the constrained (low powered, low computation, less size, etc.) networks with the protocol 6LoWPAN (IPv6 Low Powered wireless Personal Area Networks). Due to the constrained behaviour of the RPL protocol, it will leads to many RPL routing attacks such as Sinkhole, Black hole, Wormhole, Selective forwarding, rank attacks, etc. This paper was focused on the Wormhole attack. The Wormhole attack will select the packets from one location and drops those packets in some other location (malicious) by forming the Tunnelling. To detect this attack here proposed and implemented a novel approach called (ADWA). Acknowledgement based technique for detection of the wormhole attack in RPL based Internet of Things networks. This approach was shown efficient results with the Telosb sky emulator nodes in the Contiki Cooja simulator, in terms of the Packet delivery ratio, delay and detection of wormhole attack.