Cube Slam is a Chrome Experiment built with WebRTC, an open web technology that lets you communicate in real-time in the browser (and in this case, play an old-school arcade game with your friends) without downloading and installing any plug-ins. In this post, we wanted to explain a bit about how Cube Slam works.
Cube Slam uses getUserMedia to access your webcam and microphone (with your permission, of course), RTCPeerConnection to stream your video to a friend, and RTCDataChannel to transfer the bits that keep the gameplay in sync. If you and your friend are behind firewalls, RTCPeerConnection uses a TURN relay server (hosted on Google Compute Engine) to make the connection. When there are no firewalls in the way, however, the entire game happens directly peer-to-peer, reducing latency for players and server costs for developers.
Cube Slam is the first large-scale application to use RTCDataChannel, which provides an API similar to WebSocket, but sends the data over the RTCPeerConnection peer-to-peer link. RTCDataChannel sends data securely, and supports an "unreliable" mode for cases where you want high performance but don't care about every single packet making it across the network. In cases like games where low delay often matters more than perfect delivery, this ensures that a single stray packet doesn't slow down the whole app.
RTCDataChannel only supports unreliable mode in desktop Chrome today. We're working on implementing the latest WebRTC spec, where we'll use the standard SCTP protocol to support reliable mode. WebRTC will also be available on Chrome for Android later this year, and you can try it now by flipping “Enable WebRTC Android” in chrome://flags. Several browsers are currently working on implementing WebRTC, and we’re looking forward to the day when you can have a Cube Slam face-off against your friends on any browser and any device.
To learn more about the tech in Cube Slam, you can check out our technology page and source code. Disable the shields! Destroy the screen! Have fun!
Justin Uberti is one of the co-creators of the WebRTC initiative, and leads the WebRTC engineering team at Google. Previously, Justin helped create Google+ Hangouts.
Posted by Ashleigh Rentz, Editor Emerita