How to develop services for Ubuntu phone / tablet?

Hello,

Application focus seem to be on foreground apps with UI, at least from what I've gleaned on the web pages (HTML, Qt, etc.).

Is there a way to develop background services? Where the UI makes use of the service.

Is it possible and how would a background service be coded?

Many Thanks, Caesar.

Ideally, your UI should be in small UI-specific apps, and all your real heavy lifting logic and core functions should be in a headless background service.

Background services can be written in any language. They can be written in a different language than the UI process (the current favorite UI language is QML).

Background services communicate with UI processes using dbus. dbus is the generally-accepted public (and discoverable) way to expose a service API. dbus bindings exist for most languages.

Your background services should usually run as root...unless your service has a network connection or other security issue. Then your service should run as a separate system user (not you, not root).

Always-on daemons generally start at boot (using an Upstart .conf file or systemd .service file), and supervised and respawned by init (if needed). On-demand services are generally started by dbus when called (using a dbus .service file).

You can listen to dbus using the d-feet package, among others. One good example of an always-on service with multiple clients and a public API is evolution-data-server. Another is Network Manager.

EXAMPLE UI CLIENT Runs as user Starts when user clicks on it Written in favorite UI language Communicates with service using dbus or pipes or sockets Communicates with other services using dbus

EXAMPLE BACKGROUND SERVICE Runs as root Totally headless - output to logfiles. Console output only for debugging. Written in any language you like Communicates with your client using dbus or pipes or sockets Communicates with other system and user services (Network Manager, Geolocation, Calendar, Contacts, Power Manager, etc) using dbus dbus API means other clients and services can query your service Started by dbus upon first request from a client or another service

Thank you Ian! Specifically, can I write it using Java? (is there a Java runtime equivalent to say OpenJDK?)