Introduction: Full-stack Hello World for Kotlin Multiplatform
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A full-stack hello world for Kotlin Multiplatform

Project Structure

This project consists of several gradle modules as well as an xcode project. It was developed using Intellij IDEA but is probably usable from Android Studio as well.


This is the central module which is included in both server and client. It consists of a Message class which is serializable by kotlinx-serialization.


This is a simple Ktor server running on the Netty engine with a single endpoint /message, which outputs a Message object serialized to JSON.

Running ./gradlew server:run will deploy the server to localhost on port 8080.


This consumes the shared module and contains shared client code. It includes an ApiClient class with a method to query the /message endpoint using the Ktor http client, as well as a top-level function hello() which provides a callback interface and rudimentary error-handling.


This is an Android project consuming the :shared-mobile module. It contains a single activity which calls the hello() function and displays its output in UI.

The Android app can be built by creating and running an Android run configuration in IDEA.

Because the server deploys to localhost, it's recommended to only run the app through the emulator. There is configuration to ensure that the emulator sees the local server deploy which will not work on-device.


The iOS code lives in the ios directory. It includes a ViewController which calls the hello() function and renders its output to screen.

The iOS code can be modified or built by opening ios/Multiplatform Hello.xcodeproj in Xcode.

Because the server deploys to localhost, it's recommended to only run the app through the simulator, but there is gradle configuration for device targets as well.


There is a browser client available in the :browser module. It contains a simple page which calls hello() and updates the page body with the output.

The browser client can be deployed with ./gradlew browser:browserRun. It will deploy to localhost on port 8081 to avoid interfering with the server on 8080.


Unit tests exist for the :shared, :shared-client, and :server modules. They can be run using the gradle task check. You may need to clean as well in order to re-run tests if no code-changes have happened.

Known issues

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