Worker functions take a single parameter which is the message to be received. To obtain a port, you need to call the spawn(target) function of a worker environment, as in:

let env = WorkerEnvironment.builder(): withFixedThreadPool()
let port = env: spawn(|message| -> println(">>> " + message))

A port provides a send(message) method:

port: send("hello"): send("world")

Messages are being put in a queue, and eventually dispatched to the function that we spawned.