iPhone's missing link: Push service brings two-way life to smartphone

Apple’s missing link for the iPhone has been a two-way connection with the cloud. With its new push notification service, Apple enables greater interactivity for the handset’s applications and users.

But at the same time, the Apple Push Notification Service (APNS) highlights the way Apple’s ban on background processing and multitasking still hamstrings the iPhone’s two-way interaction with the Web. 

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APNS lets an iPhone application register to receive remote updates. Those updates might be a new tweet on Twitter, an item added to newsfeed, or a challenge from an online game player. APNS sends the update directly to the registered iPhone. The update can trigger a sound, show a text message, or prepare an iPhone app to launch in response.

It’s already been quickly implemented by iPhone game vendor Tapulous, with the help of start-up Urban Airship, which is kind of an APNS middleman.

The new API is part of Apple’s version 3.0 of the iPhone operating system released earlier this summer.

But push comes at a cost -- not for users but developers.

The service requires creating and maintaining a server, or group of servers, that is constantly linked with the Apple server farm to process the message requests. It’s a daunting requirement for many small software developers, who also may lack experience in handling socket connection pools. And the new service has revived rather than muted some complaints that Apple still won’t permit apps on the iPhone to run at the same time in the background and make periodic checks for information updates.

Apple’s argument is that background processing and multitasking can consume CPU cycles and memory resources and exhaust the battery. With a push system, iPhone apps in effect are asleep, and the user wakes each one up separately to respond to a relevant notification.

Early impressions

Back in April, bloggers such as Mobile Orchard’s Ryan Daigle (formerly a principal with Y Factorial, which merged with iPhone and web application developer DigitalToniq) noted the complexities of APNS.

In a blog post, Daigle notes that APNS relies on socket connections to deliver messages to the Apple gateway, which is set up similarly to an SMS gateway: a raw binary interface via long-lived or persistent socket connections. By themselves, sockets are “not that intimidating,” he writes, but it does add complexity for developers who don’t have experience in maintaining a server-based pool of connections. (Enterprise developers, with experience in server-side persistent or long-running applications in Java or similar languages, will find this much less of a challenge, he says.)

Developers will need to get the right tools and “think about this before designing their iPhone apps [with APNS],” he added.

All those issues remain, Daigle says today. “As a push notification implementation, APNS is robust, and architected to be highly performant,” he says. “However, in its usage, it is flawed in that many apps are using push as a workaround to missing functionality on the iPhone.”