Ktor server

Learn HTTP servers with Ktor server.

What is Ktor server?

Ktor server is a coroutine based framework for writing HTTP servers in Kotlin. It works with engines like Netty, Jetty or CIO.

A server is started with the embeddedServer function. Example: embeddedServer(Netty, port = 8080) { ... }.start(wait = true). Routing and plugins are declared inside this block. Because it is coroutine based, each request is handled as a coroutine; this differs from a thread per request model. In this lesson you will set up the basic server skeleton.

Engine choice

A Ktor server runs on an engine. On JVM the common choices are Netty, Jetty and CIO.

The engine handles sockets and request dispatch. In embeddedServer(Netty, port = 8080) { ... } the engine is the first parameter. Netty is a common, mature choice for production. CIO is written in Kotlin and needs no extra dependency. The choice depends on performance and dependency needs.

Exercise Set up the server skeleton

Define a server with val server = embeddedServer(Netty, port = 8080) { }. Print println("Server ready").

Show example solution

fun main() {
    val server = embeddedServer(Netty, port = 8080) {
    }
    println("Server ready")
}

Test yourself

How is a Ktor server started?
- main()
- HttpClient()
- embeddedServer()
- runBlocking()
Show answer

embeddedServer() — The embeddedServer function starts the server.

Complete the embeddedServer call

val server = ____(Netty, port = 8080) {
    
}

Show answer

val server = embeddedServer(Netty, port = 8080) {
    
}

Match Ktor server parts

embeddedServer

Starts server
Netty

Engine
port

Port number
routing

Route definition

Next lesson: Routing

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