Vala D-Bus Client Examples

These examples require Vala >= 0.9.2 and GLib/GIO >= 2.26

Rules for writing Vala D-Bus interfaces:

  • annotate the interface with [DBus (name = "...")]

  • convert DBusCamelCaseNames to vala_lower_case_names

  • add throws IOError to each interface method

BlueZ - Bluetooth Discovery

[DBus (name = "org.bluez.Adapter")]
interface Bluez : Object {
    public signal void discovery_started ();
    public signal void discovery_completed ();
    public signal void remote_device_found (string address, uint klass, int rssi);
    public signal void remote_name_updated (string address, string name);

    public abstract void discover_devices () throws IOError;
}

MainLoop loop;

void on_remote_device_found (string address, uint klass, int rssi) {
    stdout.printf ("Remote device found (%s, %u, %d)\n",
                   address, klass, rssi);
}

void on_discovery_started () {
    stdout.printf ("Discovery started\n");
}

void on_remote_name_updated (string address, string name) {
    stdout.printf ("Remote name updated (%s, %s)\n", address, name);
}

void on_discovery_completed () {
    stdout.printf ("Discovery completed\n");
    loop.quit ();
}

int main () {
    Bluez bluez;
    try {
        bluez = Bus.get_proxy_sync (BusType.SYSTEM, "org.bluez",
                                                          "/org/bluez/hci0");

        // Connect to D-Bus signals
        bluez.remote_device_found.connect (on_remote_device_found);
        bluez.discovery_started.connect (on_discovery_started);
        bluez.discovery_completed.connect (on_discovery_completed);
        bluez.remote_name_updated.connect (on_remote_name_updated);

        // Async D-Bus call
        bluez.discover_devices ();
    } catch (IOError e) {
        stderr.printf ("%s\n", e.message);
        return 1;
    }

    loop = new MainLoop ();
    loop.run ();

    return 0;
}

Compile and Run

$ valac --pkg gio-2.0 dbus-bluez.vala
$ ./dbus-bluez

Purple - Instant Messaging

[DBus (name = "im.pidgin.purple.PurpleInterface")]
interface Purple : Object {
    public signal void received_im_msg (int account, string sender, string msg,
                                        int conv, uint flags);

    public abstract int[] purple_accounts_get_all_active () throws IOError;
    public abstract string purple_account_get_username (int account) throws IOError;
}

int main () {
    try {
        Purple purple = Bus.get_proxy_sync (BusType.SESSION,
                                            "im.pidgin.purple.PurpleService",
                                            "/im/pidgin/purple/PurpleObject");

        var accounts = purple.purple_accounts_get_all_active ();
        foreach (int account in accounts) {
            string username = purple.purple_account_get_username (account);
            stdout.printf ("Account %s\n", username);
        }

        purple.received_im_msg.connect ((account, sender, msg) => {
            stdout.printf (@"Message received $sender: $msg\n");
        });

        var loop = new MainLoop ();
        loop.run ();

    } catch (IOError e) {
        stderr.printf ("%s\n", e.message);
        return 1;
    }

    return 0;
}

Compile and Run

$ valac --pkg gio-2.0 dbus-purple.vala
$ ./dbus-purple

Skype status client

[DBus (name = "com.Skype.API")]
interface Skype : Object {
    public abstract string invoke (string cmd) throws IOError;
}

string send (Skype skype, string cmd) throws IOError {
    return skype.invoke (cmd);
}

void send_check (Skype skype, string cmd, string expected) throws IOError {
    string actual = send (skype, cmd);
    if (actual != expected) {
        stderr.printf ("Bad result '%s', expected '%s'\n", actual, expected);
    }
}

int main (string[] args) {
    try {

        Skype skype = Bus.get_proxy_sync (BusType.SESSION,
                                          "com.Skype.API", "/com/Skype");

        send_check (skype, "NAME skype-status-client", "OK");
        send_check (skype, "PROTOCOL 2", "PROTOCOL 2");

        // if no arguments given, show current status, otherwise update
        // status to first argument
        if (args.length < 2) {
            stdout.printf ("%s\n", send (skype, "GET USERSTATUS"));
        } else {
            // possible statuses: ONLINE OFFLINE SKYPEME AWAY NA DND INVISIBLE
            send_check (skype, "SET USERSTATUS " + args[1], "USERSTATUS " + args[1]);
        }

    } catch (IOError e) {
        stderr.printf ("%s\n", e.message);
        return 1;
    }

    return 0;
}

Compile and Run

$ valac --pkg gio-2.0 dbus-skype.vala
$ ./dbus-skype
USERSTATUS ONLINE
$ ./dbus-skype AWAY
$ ./dbus-skype
USERSTATUS AWAY

Waiting for a service to become available (outdated example)

Waiting for a service to become available (outdated example)

Generating a vala interface from an existing DBus interface

When making an interface based on an existing DBus interface the vala-dbus-binding-tool can be used. This tool will create a interface based on an XML-file describing the DBus interface. For objects that implement the introspectable interface this file is easy to obtain. use dbus-send to get the XML printed to the screen

dbus-send --print-reply --type=method_call --dest=busname objectpath org.freedesktop.DBus.Introspectable.Introspect

alternatively d-foot can be used as a gui to browse DBus and send commands. The vala-dbus-binding-tool can be used on the obtained XML file. In it’s most basic form the command looks like this:

vala-dbus-binding-tool --api-path=”path_to_xml_file”

This will create a vala file for all interfaces provided by the object.


Vala/Examples

Projects/Vala/DBusClientSamples (last edited 2016-06-23 10:59:14 by JoostFock)