I'm currently trying to come up with a good multiplatform socket API. On the JS/Node side there is s...

# javascript

[Edoardo Luppi]

I'm currently trying to come up with a good multiplatform socket API.
On the JS/Node side there is some trade off in terms of internal implementation

actual fun connect(host: String, port: Int, listener: Result<ServerProperties>) {
  GlobalScope.launch {
    connectAsync(port, host).await()            // Await a JS promise
    val length = readUnsignedIntAsync().await() // Await a JS promise
    val data = readStringAsync(length).await()  // Await a JS promise
    val serverProperties = ServerProperties(data)
    listener.onSuccess(serverProperties)
  }
}

Would the above code be considered "ok"?

[turansky]

connectAsync - custom function?

[Edoardo Luppi]

@turansky yes, it's a function that return a Promise, that I coded myself in Kotlin

[turansky]

Why it’s not suspend fun?

[Edoardo Luppi]

@turansky it uses the Node's Socket class, this is it

private fun connectAsync(port: Int, host: String): Promise<Any?> =
  Promise { resolve, reject ->
    val errorHandler: (Error) -> Unit = {
      socket.removeAllListeners(Event.CONNECT)
      reject(it)
    }
    val connectHandler = {
      socket.removeListener(Event.ERROR, errorHandler)
      resolve(null)
    }
    socket.once(Event.ERROR, errorHandler)
    socket.setKeepAlive(true)
    socket.setTimeout(1000)
    socket.connect(port, host, connectHandler)
  }

[Edoardo Luppi]

Not sure if it's doable with coroutines

[turansky]

It’s definetely possible 🙂

[turansky]

Even more elegant

[turansky]

cc @Sergei Grishchenko

[Edoardo Luppi]

Maybe I'm too new to coroutines, totally possible

[Edoardo Luppi]

maybe using suspendCancellableCoroutine is an option? So I don't have to use the JS promise

[Edoardo Luppi]

New version of connectAsync. This avoids using await, and propagating the same concept to writing and reading bytes avoids the Promise's then usages

private suspend fun connectAsync(port: Int, host: String) {
  suspendCancellableCoroutine { continuation ->
    val errorHandler: (Error) -> Unit = {
      socket.removeAllListeners(Event.CONNECT)
      continuation.resumeWithException(it)
    }

    val connectHandler = {
      socket.removeListener(Event.ERROR, errorHandler)
      continuation.resume(Unit)
    }

    socket.once(Event.ERROR, errorHandler)
    socket.setKeepAlive(true)
    socket.setTimeout(1000)
    socket.connect(port, host, connectHandler)
  }
}

[Edoardo Luppi]

Is that what you meant when you said it was possible? Just for confirmation that I'm not doing wrong stuff lol

[turansky]

on and once - can open suspend API without callbacks

[Edoardo Luppi]

@turansky so like this in KT?

EventEmitter.once(socket, Event.ERROR)

[Edoardo Luppi]

image.png

[turansky]

Probably TS types are outdated

[turansky]

Also I saw on and once on the same level with EventEmitter (not checked)

[turansky]

PR also will be fine 🙂