sdbus-kotlin

sdbus-kotlin is a direct port of sdbus-c++ to kotlin/native. Once the port completed, some kotlinization of the APIs has begun, but is definitely not complete or API stable. sdbus-kotlin also contains a code generator, which will generate kotlin adaptors or proxies for dbus xml interfaces provided.

Currently sdbus-kotlin is only built for linuxX64, but the goal is to bring it to arm64 next, and any other possible platforms after.

Getting Started

While sdbus-kotlin can be used directly without the generator, it can be a bit cumbersome to manage the types and wrappers. Its recommended to use the codegenerator whenever possible.

Code Generation

There is a gradle plugin which can generate sources as part of the the build when given xml files.

plugins {
    ...
    id("com.monkopedia.sdbus.plugin") version "<version>"
}

sdbus {
    sources.srcDirs("src/dbusMain")
    outputs.add("linuxX64Main")
    generateProxies = true
    generateAdapters = true
}
...

This will generate the proxies and adapters for any interfaces declared in src/dbusMain and make them available from the linuxX64Main sources.

Build Setup

To access the APIs, make sure the module depends on sdbus-kotlin. While the API is available as a common kotlin module, its implementations are currently only for linuxX64 and linuxArm64.

val nativeMain by getting {
    dependencies {
       implementation("com.monkopedia:sdbus-kotlin:0.3.0")
    }
}

Since sdbus-kotlin compiles against libsystemd, you have to specify some extra flags for the linker to be successful. Generally, this is just allowing the linker access to your system libs, but alse be sure your system has libsystemd matching or newer than sdbus-kotlin (currently 257.3).

compilerOptions {
    freeCompilerArgs.set(listOf("-linker-options", "-L /usr/lib"))
}

Lastly, if using any complex types, their serialization in managed using kotlinx-serialization, so that must be applied as well.

plugins {
    kotlin("multiplatform") version "2.1.0"
    kotlin("plugin.serialization") version "2.1.0"
}

For a full example build file, see the bluez-scan sample.

API

There are a number of create*Connection methods which can be used to get a connection to dbus. If the application is only interacting with one service, it may be worth using the withService to have a default service.

val connection = createSystemBusConnection().withService(ServiceName("org.bluez"))

Then the connection can be used to create proxies or adaptors as needed. Some core dbus interfaces are provided with nicer implementations (e.g. ObjectManagerProxy).

val adapter = Adapter1Proxy(connection.createProxy(ObjectPath("/org/bluez/hci0")))
adapter.startDiscovery()

See the full API docs for more information.

Complex Types

If not using the code generator, then complex types can be defined using kotlinx-serialization. Native types will be translated into native dbus types, and lists/maps will be automatically handled as well.

@Serializable
public data class AcquireType(
  public val fd: UnixFd,
  public val mtu: UShort,
)