CLI instant messenger in 60 lines with ZMQ

client.kt

package chat

import org.zeromq.ZMQ
import kotlin.concurrent.thread

fun main(args: Array<String>): Unit =
    ZMQ.context(1).use { ctx ->
      thread {
        ctx.socket(ZMQ.SUB).use { stream ->
          stream.connect(MESSAGE_STREAM)
          stream.subscribe(ByteArray(0))

          while (true) {
            val msg = stream.recvStr()

            println("client got $msg")
          }
        }
      }

      ctx.socket(ZMQ.PUSH).use { push ->
        push.connect(POST_MESSAGE)

        while (true) {
          val msg = readLine()

          println("will send $msg")

          push.send(msg)
        }
      }
    }

lib.kt

package chat

val POST_MESSAGE = "tcp://localhost:6573"
val MESSAGE_STREAM = "tcp://localhost:6574"

server.kt

package chat

import org.zeromq.ZMQ

fun main(args: Array<String>): Unit =
    ZMQ.context(1).use { ctx ->
      ctx.socket(ZMQ.PULL).use { post ->
        post.bind(POST_MESSAGE)

        ctx.socket(ZMQ.PUB).use { stream ->
          stream.bind(MESSAGE_STREAM)

          while (true) {
            val msg = post.recvStr()

            println("server got $msg")

            stream.send(msg)
          }
        }
      }
    }