D-Bus is now largely used in a lot of applications for language-independant, object-oriented RPC system.
The erlang platform needs an erlang native implementation.
This example is making a dbus call to the org.freedesktop.DBus system service (under linux) and a list of registered services.
{ok, Bus} = dbus_bus_reg:get_bus(session),
{ok, Service} = dbus_bus:get_service(Bus, 'org.freedesktop.DBus'),
{ok, RemoteObject} = dbus_remote_service:get_object(Service, '/org/freedesktop/DBus'),
{ok, Iface} = dbus_proxy:interface(RemoteObject, 'org.freedesktop.DBus'),
{ok, Names} = dbus_proxy:call(Iface, 'ListNames', []),
io:format("ListNames: ~p~n", [lists:sort(Names)]),
ok = dbus_remote_service:release_object(Service, RemoteObject),
ok = dbus_bus:release_service(Bus, Service),In the demo folder there is a bigger example, but is a minimal service callback module:
-module(my_service).
-include_lib("dbus/include/dbus.hrl").
-behaviour(gen_dbus).
-export([
%% api
start_link/2,
handle_info/2,
%% dbus object callbacks
'HelloWorld'/1,
'HelloWorld'/3,
%% gen_dbus callbacks
init/1
]).
-record(state, {}).
start_link() ->
gen_dbus:start_link({local, ?MODULE}, ?MODULE, [], []).
init([Service, Path]) ->
State = #state{},
Methods = ['HelloWorld'],
{ok, {"com.example.MyService", '/SomeObject', [
{interface, 'com.example.MyInterface'},
{methods, Methods},
{signals, []}
]}, State}.
'HelloWorld'(dbus_info) ->
[{interface, 'com.example.MyInterface'},
{signature, [string], [{array, string}]}].
'HelloWorld'([HelloMessage], From, State) ->
{reply, ["Hello from Erlang"], State}.
handle_info(Info, State) ->
error_logger:warning_msg("Unhandled info: ~p~n", [Info]),
{noreply, State}.
When the dbus application is running you can start this service with my_module:start_link(). or add it to your supervision tree.
Caveat at the moment the service creation does not open a dbus connection and as a result the service will not be visible until you create the first dbus connection e.g. via dbus_bus_reg:get_bus(session).
The status:
- Consuming D-Bus services: ok
- Providing D-Bus services: ok
- Tests for both are working!
- Connect through TCP and UNIX socket: ok
- Figure out why
make cttests don't run on github actions - Fix signal emission from services
- Make dializer happy
- Some authentication mechanisms are not implemented, but architectures allows for easy extension (see https://github.com/lizenn/erlang-dbus/blob/master/src/dbus_auth_cookie_sha1.erl, https://github.com/lizenn/erlang-dbus/blob/master/src/dbus_auth_external.erl and https://github.com/lizenn/erlang-dbus/blob/master/src/dbus_auth_anonymous.erl)
- Create new gen_dbus.erl that uses
handle_dbus_call(Name, Args)form instead of current. - Cleanup Supervisor & gen_server hierarchy
- Remove superfluos gen_servers (proxy / peer / dbus)
- Make service registration more explicit when using multiple busses
- Fix indentation
- More docs & examples
- More tests: unit tests regarding (un)marshaling would be really great, even if the above mentioned xample has rather complex interfaces which works both with Python and Java implementations
- Provide facilities for standard interfaces: Properties, ObjectManager, etc.