A huge momentum towards IP enabled Wireless Sensor Networks (WSN) appeared through the emerging 6LoW-PAN protocols (i.e. IPv6 over Low power Wireless Personal Area Networks). By usage of existing cross domain open standards in contrast of proprietary solutions, deployments of WSNs are not tailored too tight for specific applications. Nevertheless, 6LoWPAN is only the first step for the usage of internet protocols in WSNs. Still efforts on higher layers on top of 6LoWPAN are an urgent need to provide seamless connectivity and interaction of highly resource constrained devices with higher valued services. This paper describes a new approach to bind SOAP to the emerging Constrained Application Protocol (CoAP) protocol. Thereby CoAP provides a lightweight but reliable transport binding for SOAP based protocols. Compared to the widespread TCP based HTTP binding, round trip times can be reduced by 43% in an exemplary scenario. Combined with dedicated XML compressors like the Efficient XML Interchange format (EXI), existing heavy weight SOAP based protocols become also applicable in WSNs.