The ZeroTier SDK: P2P Apps With Standard Protocols

As of this week it is now possible to connect desktop and mobile apps to virtual networks with the ZeroTier SDK. With our SDK applications can now communicate peer to peer with other instances of themselves, other apps, and devices using standard network protocols and with only minimal changes to existing network code. (On some platforms no changes at all are required.) The SDK repository at GitHub contains documentation and example integrations for iOS, Android, and the Unity game engine for in-game peer to peer networking using ZeroTier.

The ZeroTier SDK is an evolution of what we formerly called Network Containers, and still supports the same Linux network stack interposition use case. It’s still beta so do not expect perfection. We are innovating here so excuse the dust.

A Less WIMPy Path to Peer-to-Peer Networking

Most existing P2P apps either engineer their own special-purpose protocols from the ground up or use one or more P2P networking libraries, but in both cases P2P communication is done using a protocol stack and deployment that is peculiar to the app and can only easily interoperate with other instances of the same app. This extends the “WIMP model” of computing (“weakly interacting massive programs,” a play on the hypothetical “weakly interacting massive particle” from physics) into network space yielding programs that cannot interoperate directly.

This makes it hard to build true ecosystems where many programs can combine to provide exponentially increasing value at higher levels. It also means that peer to peer networking is a “special snowflake” in your development process, requiring special code, special protocols, etc. that are wholly different from the ones your app uses to communicate with the cloud. This is one reason many apps simply skip on peer to peer. Why build the app’s networking features twice?

The ZeroTier SDK takes a different approach. It combines a lightweight TCP/IP stack (currently LWIP) with the ZeroTier network virtualization core to yield a “P2P library” that tries to be invisible. Our SDK allows apps to connect to each other using the same protocols (and usually the same code) they might use to connect to a cloud server or anything else on a TCP/IP network.

Since ZeroTier also runs on servers, desktops, laptops, mobile devices, containers, embedded/IoT “things,” etc., an app using the ZeroTier SDK can also freely communicate peer to peer with all of these.

The ZeroTier SDK lives entirely in the app. No elevated permissions, kernel-mode code or drivers, or other special treatment by the operating system is needed. This means that P2P apps speaking standard interoperable native network protocols can be shipped in mobile app stores without special entitlements or other hassles.

A Hypothetical Ecosystem

To understand what the ZeroTier SDK enables it helps to imagine how it might be used.

Let’s start by imagining an augmented reality game similar to Pokémon Go. The app is built with the ZeroTier SDK, and all instances of the app join a public virtual network and communicate directly to one another using HTTP and a RESTful API internal to the app. This allows instances of the app to exchange state information directly with lower latency (and at lower cost to the app’s developer) than relaying it through cloud servers.

Now the maker of the game does something interesting: they document the game’s peer to peer RESTful API and allow third party clients to obtain authentication tokens to communicate with running game instances.

Since the application peer to peer network runs ZeroTier, anything else can join it. This includes but is not limited to servers, desktops, laptops, IoT devices, and so on. Developers can now build scoreboards, web apps, secondary or “meta” games, team communication software, or virtually anything else they can imagine. Since these apps can communicate with actual instances of the game in real time, interoperation with the game ecosystem can be extremely fast and extremely rich. Since the game developer does not have to carry all this traffic over a proprietary cloud this introduces no additional cost burden.

Fast forward a year and there are IoT light bulbs that light up when players are near (with sub-50ms responsiveness), new PC games that extend the augmented reality experience provided by the mobile app into virtual reality worlds, and advanced players have written their own software to help their teams organize and cooperate together.

Beta Testers Wanted

The ZeroTier SDK is in beta and we’re still working to perfect integration on a variety of platforms. Right now we are looking for app and game developers who are interested in working with us. If you just want to take a look feel free to pull the code, but if your interest is more serious drop an e-mail to contact@zerotier.com and we’d be happy to work with you and help you out.