Http Server in Kotlin

Here’s the translation of the HTTP Server example from Go to Kotlin:

Our HTTP server example demonstrates how to create a basic server using the ktor framework.

import io.ktor.application.*
import io.ktor.http.*
import io.ktor.response.*
import io.ktor.routing.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*

fun main() {
    embeddedServer(Netty, port = 8090) {
        routing {
            get("/hello") {
                call.respondText("hello\n")
            }
            
            get("/headers") {
                val response = call.request.headers.entries().joinToString("\n") { (name, values) ->
                    values.joinToString("\n") { value ->
                        "$name: $value"
                    }
                }
                call.respondText(response)
            }
        }
    }.start(wait = true)
}

In Kotlin, we use the Ktor framework to create HTTP servers. Ktor provides a simple and expressive way to define routes and handle requests.

We define two routes in our server:

1. The /hello route, which responds with a simple “hello” message.
2. The /headers route, which echoes all the HTTP request headers back in the response.

The embeddedServer function is used to start the server. We specify Netty as the engine and set the port to 8090.

Inside the routing block, we define our routes using the get function, which corresponds to HTTP GET requests.

For the /headers route, we iterate through all the headers in the request and format them as a string to be sent back in the response.

To run the server:

$ kotlinc -cp ktor.jar http-server.kt -include-runtime -d http-server.jar
$ java -jar http-server.jar &

Now you can access the server:

$ curl localhost:8090/hello
hello

$ curl localhost:8090/headers
User-Agent: curl/7.68.0
Accept: */*

This example demonstrates how to create a basic HTTP server in Kotlin using the Ktor framework, defining routes and handling requests.