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

The code generation tool can be found as a jar attached to the latest release.

java -jar codegen-all-0.1.0.jar --help
Usage: xml2kotlin [<options>] <input>

Options:
  -o, --output=<path>  Output directory
  -k, --keep           Do not delete existing content in output
  -a, --adaptor        Generate the code for an adaptor
  -p, --proxy          Generate the code for a proxy
  -h, --help           Show this message and exit

By default, the code generator will delete all other files in the output directory before generating, so be sure to use -k if generating multiple interfaces separately.

$ java -jar codegen-all-0.1.0.jar -k -p -o src/nativeMain/kotlin/generated src/dbusMain/Adapter1.xml

Build Setup

Currently, there is no plugin to aid in configuring gradle, so a few steps are needed to use sdbus-kotlin. The simple part is depending on the library.

val nativeMain by getting {
    dependencies {
       implementation("com.monkopedia:sdbus-kotlin:0.1.0")
    }
}

Since sdbus-kotlin compiles against libsystemd, you have to specify some extra flags for the linker to be successful. Make sure your system has libsystemd matching or newer than sdbus-kotlin (currently 256.2).

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

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

plugins {
    kotlin("multiplatform") version "2.0.0"
    kotlin("plugin.serialization") version "2.0.0"
}

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,
)