About Announcements enables a device or app to announce itself on the AllJoyn™ network for other devices and apps to discover. The following information is shared:
- App and Device Friendly Names
- Make, Model, Version, Description
- Supported Languages
- App Icon
- Supported objects and interfaces
- Service Port number
- App and Device unique identifiers
For a complete list, refer to the Interface Definiton.
The About feature supports multiple languages, so the client can display the language that is most appropriate for the user. With the About feature, a client can discover devices and apps on the network, get some meta data about the device/app, discover the services it supports, and get an icon to represent the device/app.
Concepts and Terminology
Generally speaking, there are two sides to the About feature:
- About Server. This is the device or app that is announcing itself.
- About Client. This is the device or app that is discovering apps/devices.
How It Works
Here's roughly what happens behind the scenes:
An About Server announces itself by sending a sessionless signal including: the session port, list of objects and interfaces; and a subset of the About Announcement information, including App and Device Name, default language, App and Device unique identiers.
An About Client discovers the sessionless signal, which includes the information listed above. The client can now display some information about the discovered device/app, App/Device Name and supported services.
Optionally, the About Client can connect to the app/device's About Server on the service port to extract more information. Typically, this is done to get the app icon.