An Internet of Things (IoT) system features integration information from heterogeneous sensor devices, allowing them to deliver a variety of sensed information through networks. An IoT broker in the system acts as an information exchange center, relaying periodic messages from heterogeneous sensor devices to IoT clients. As more devices participate in the IoT system, the service scale of entire system increases. To overcome the limitation of the number of direct links to an single working element, the whole IoT system should be divided into many subsystems, called IoT units, to form the system hierarchy. Furthermore, applying the service-oriented architecture (SOA) concept to realize the IoT service can facilitate to adapt the future-proof devices to the IoT system. Normally, a web-based message visualization can unify the client interface in a SOA based system. However, a large volume of web-based messages with various sizes are not easy to be stably displayed at the client side. This paper proposes an IoT system skeleton and a shortest processing time (SPT) algorithm for scheduling web-based IoT messages. The implemented scheduling scheme supported by a priority queue model can effectively stablize the response messages from the scattered IoT sensors per each client request.