New Business Mobile SIP Clients and iOS 4 Limitations

A little over a month ago, we wrote up a review of the Acrobits Softphone, a mobile SIP client for the iPhone clearly made for the everyday consumer. It was great for making and receiving calls (with push notifications enabled), but the functionality stopped there. I ranted for a while about the state of mobile VoIP applications, gave the app a ‘good for what it is made for’ review, and called it quits.

A lot has changed in only a couple of weeks.

First off, iOS 4 was released, and the new iPhone 4 came out only a few days later. The most anticipated feature—for me, at least – is multitasking. I’ve been waiting for months for a way to get incoming calls on my iPhone SIP clients without having to rely on push notifications and third party servers.

Second, Acrobits announced the business version of their softphone, claiming that their new app is the “first mobile SIP client capable of replacing your desktop phone.” We managed to get our hands on the invitation-only first release of the ‘Acrobits Softphone Business Edition’, and I have been putting it through all the usual tests I do with desk phones. I’m not going to do a full review of the app just yet since a lot may change before it goes public. Some of the new features include:</>

• Blind and Attended Transfer, essential for any business SIP client
• Multi-line support
• Call Waiting
• Conferencing
• Included G.729 and G.722 wideband codec

Also included are some aesthetic and UI changes.

Consumer Version	Business Version

Consumer Version	Business Version

Acrobits is also working on perfecting multitasking background support. It already works to some extent. You can go to the iPhone home screen or other applications without terminating an ongoing call. A small red ‘Softphone’ bar appears at the top of your screen that will take you back to the Acrobits app when pressed.

You can see above that a call is still in progress when browsing Youtube.

So everything’s great, right?

Not quite.

Acrobits is doing a fine job with their new product but it looks like Apple is limiting background wakeup in iOS 4 to only work if TCP is selected as the SIP transport type. This means that VoIP applications running in the background only respond if incoming traffic arrives in the TCP socket. Although standards based SIP providers should be unaffected, many services currently do not support TCP.