Question

(The following question is for mobile platforms in general (iPhone, Android, Blackberry))

We are integrating chat functionality into our existing application. I designed the system with a .Net web service and Sql Database to keep track of chat messages. Everything’s working fine so far, when the chat window is open.

I need a way to notify the user of a new message when he/she is not currently viewing the chat screen (meaning either the app is not in the foreground or they are in another section of the app (not the chat screen).

Obviously, push notifications would be perfect here, but I’m not sure when I should be sending pushes.

How would the client sending the message know whether or not the other guy is viewing the chat screen? Should I just be sending pushed with every single message and have the receiving device decide whether or not it needs to pop up a window or display something in a nofication bar?

It seems like overkill to be pushing every single time a message is sent. How is this normally done?

Any ideas at all would be greatly appreciated.

Thanks.

Answer 1

First and foremost, keep in mind that your server will act as the broker for all messages passed between different chat clients. Here’s how this could work:

• User A initiates a message for user B
• Message gets sent to the server.
• Server determines that this message is for user B.
• Server initiates a push notification and delivers the message to user B.

Now why would you need to push every single chat message? Because the only other way for your users to get notified would be to poll your server for new messages. Constant polling (at whatever rate you determine) is extremely bad in the mobile realm due to limited resources (battery, networking, etc.)

In a push notification scenario, it is up to your application to handle the logic of whether the user is notified on receiving a new message. What this means is that when user B receives a new message from user A, it’s up to you to decide if you wish to notify B (i.e. bring your app to the foreground) or not. In either scenario, you want to use push notifications instead of polling.

On a similar note, user B does not necessarily have to know that user A‘s application (your app) is in the background which is why you will need to handle that logic (within your app) appropriately.