Incorporation of heterogeneous wireless sensor and actuator networks (WS&AN) is an essential challenge of web based Internet of Things (IoT) architectures. We propose to use UPnP and end-to-end HTTP communication using CoAP to bridge WS&AN and IoT system. UPnP enables automatic discovery of sensor devices which directly connect to a WS&AN via a gateway. Instead of translating WS&AN and UPnP protocols at the gateway, we propose to use CoAP in WS&AN. This provides flexible communications between sensor devices and applications. Drawback of this end-to-end Web based IoT information system is vulnerability to excessive traffics from sensor devices or from the applications because there is no authority to monitor and control traffics in the architecture. We examined the performance of our implementations to find that the transmit performance of a single sensor device could be limited by the serial communications of embedded transceiver. Excessive data requests from applications might also result in the packet loss and wasteful WS&AN congestion. If the traffic is confined within the performance limits, the implemented UPnP and ZigBee bridging using CoAP shows satisfactory performance. We can subscribe up to 16 sensor devices data with 500 msec using simple HTTP POST requests.