Hey how can a store a websocket session to send a message to the websocket later?

# ktor

[ByFloRedstone]

Hey how can a store a websocket session to send a message to the websocket later?

[bbaldino]

There was a thread related to this the other day https://kotlinlang.slack.com/archives/C0A974TJ9/p1606123821161400

[ByFloRedstone]

but i think this thread is about the client side connection i mean the server side part

[bbaldino]

Ah...what I've done for that is created a channel that messages can be added to, and the server starts a coroutine which reads from that channel and sends a message whenever there is one to read

[ByFloRedstone]

ok using the send method i have a problem to send a message because the method from where i want to send the message cant be a suspend fun wich is required from the send function

[bbaldino]

If you want your non-suspend send method to wait until the message is sent, you can run it within a runBlocking block. If you don't want to wait, you'll want to use launch on some CoroutineScope to launch a coroutine to do the send

[ByFloRedstone]

what did you mean wich "some CoroutineScope"?

[bbaldino]

Well usually you launch a coroutine from some scope you've created. GlobalScope, for example, but I don't think it's recommended to use that except for specific use cases as tasks launched there can 'leak'.

[bbaldino]

Generally though I'd say you should read through some of the coroutine tutorials on the web to get a better feel for them if you're not familiar with CoroutineScope

[ByFloRedstone]

ah ok thanks for your help

[bbaldino]

👍

[ByFloRedstone]

if i run the method its only called once. If a call it twice the second message where not send to the client

[bbaldino]

You'll need a loop

[ByFloRedstone]

really? i have a function wich is called twice! But the message where send only once.

[bbaldino]

I may not be understanding what you're describing, can you paste an example?

[ByFloRedstone]

can i send it via slack with a code box or via paste server?

[bbaldino]

You can paste it here, but I'd try and reduce it down if it's really big

[ByFloRedstone]

@EventListener
    fun onStart(e: CloudServicePreStartEvent) {
        sendNotification(SocketNotification("success", "Der Service ${e.cloudService.serviceId.name} startet"))
    }

    fun sendNotification(notification: SocketNotification) {
            webServer.notificationSockets.forEach {
                runBlocking {  it.send(Frame.Text(notification.toString())) }
            }
    }

[ByFloRedstone]

that my code so the "CloudServicePreStartEvent" is called when a server starts. While the client was connected it was called 6 times, but the client only receive on message

[bbaldino]

Did you verify the runBlocking block in sendNotification was called 6 times?

[ByFloRedstone]

Yes i was called 6 times

[bbaldino]

Ok, there might be an issue with the websocket itself, then? Maybe make sure the send is "finishing" each time it's called ?

[ByFloRedstone]

i try to print a message before and after the send and each of then was printet in the console. So i think the send method was executed

[ByFloRedstone]

is it possible, the error is on my javascript file?

let socket = new WebSocket("<wss://acp.domain.com/ws>")

socket.onopen = function (event) {
    log("info", "Connected to the Notify Socket")
}

socket.onerror = function (error) {
    log("error", error.message)
}

socket.onmessage = function (m) {
    log("message", m.data)
}

function log(type, input) {
    console.log("[NOTIFY] " + type.toUpperCase() + " | " + input)
}

[bbaldino]

I'd break on when you're doing the send and follow it through, maybe the websocket itself is closing or something?

[ByFloRedstone]

I don't think so because when closing the websocket it will be remove from the list and on next call its in the list

[bbaldino]

At this point I think you've just got to debug what's going on with the websocket