Native server

Ktor supports Kotlin/Native and allows you to run a server without an additional runtime or virtual machine. Currently, running a Ktor server under Kotlin/Native has the following limitations:

a server should be created using embeddedServer
only the CIO engine is supported
HTTPS without a reverse proxy is not supported
Windows target is not supported

Add dependencies

Ktor server in a Kotlin/Native project requires at least two dependencies: a ktor-server-core dependency and an engine dependency (CIO). The code snippet below shows how to add dependencies to the nativeMain source set in the build.gradle.kts file:

    sourceSets {
        val nativeMain by getting {
            dependencies {
                implementation("io.ktor:ktor-server-core:$ktor_version")
                implementation("io.ktor:ktor-server-cio:$ktor_version")
            }
        }
    }

To test a Native server, add the ktor-server-test-host artifact to the nativeTest source set:

    sourceSets {
        val nativeTest by getting {
            dependencies {
                implementation(kotlin("test"))
                implementation("io.ktor:ktor-server-test-host:$ktor_version")
            }
        }
    }

Configure native targets

Specify the required native targets and declare a native binary using the binaries property:

    val hostOs = System.getProperty("os.name")
    val arch = System.getProperty("os.arch")
    val nativeTarget = when {
        hostOs == "Mac OS X" && arch == "x86_64" -> macosX64("native")
        hostOs == "Mac OS X" && arch == "aarch64" -> macosArm64("native")
        hostOs == "Linux" -> linuxX64("native")
        // Other supported targets are listed here: https://ktor.io/docs/native-server.html#targets
        else -> throw GradleException("Host OS is not supported in Kotlin/Native.")
    }

    nativeTarget.apply {
        binaries {
            executable {
                entryPoint = "main"
            }
        }
    }

You can find the full example here: embedded-server-native.

Create a server

After configuring your Gradle build script, you can create a Ktor server as described here: Creating a server.

Last modified: 02 April 2024