For a basic IoT AppService sample, see the "AppServiceBlinky" sample. This sample expands on that by adding multiple clients and by having the service both send and recieve messages. 

This sample shows how you can build a single AppService that coordinates activity between multiple clients. The "NotepadService" manages a shared notpad that stores notes, allows clients to add notes, notifies clients when new notes are available, and lets the clients request all notes. To run this sample first launch the NotepadService and then launch the other samples in any order.