As discussed in the previous sections, sandboxing of the apps is achieved by running apps in different processes with different Linux identities. System services run in separate processes and have more privileges. Hence, in order to organize data and signals between these processes, an Inter-Process Communication (IPC) framework is needed. In Android, this is achieved with the use of the Binder mechanism.

The Binder framework in Android provides the capabilities required to organize all types of communication between various processes. Android application components such as Intents and content providers are also built on top of this Binder framework. Using this framework, it is possible to perform a variety of actions such as invoking methods on remote objects as if they were local, synchronous and asynchronous method invocation, and sending file descriptors across processes. Let's suppose the application in Process A wants to use certain behavior exposed by a Service that runs in Process B. In this case, Process A is the client and Process B is the service. The communication model using Binder is shown in the following screenshot: