A web application acts as a backend to process request coming from the iPhone. To send messages to iPhone from web application while processing a request(e.g., for payment), I want to send messages to iPhone when something interesting happens on the server or else if everything is successful, sending them transaction details. Which one is better to use PushSharp or SignalR? Does they both serve the same purpose? Either way, enlighten me on this topic. Its confusing to me.
SignalR is a great way to send real time information to a web client, essentially having server-side code push information to the client and call client-side code (i.e. javascript) in realtime.
PushSharp is a great way to send push notifications to native mobile apps. For iOS, this means using Apple's infrastructure. It also means that the message will be shown as a notification in the iPhone and not just inside the browser.
Essentially, if the iPhone request you mention is coming from a native app, try PushSharp. If it's a web app running in a browser, use SignalR.