Hi. Does the socket support binary data transfer?

[lemkoleg]

Does the socket support binary data transfer? ByteArray. Not ByteString

[joffrey-bion]

Yes, binary data is supported. ByteString is binary. It is to ByteArray what String is to CharArray. It's a read-only group of bytes, unlike ByteArray which is mutable.

If you really need to, you can get a ByteArray from a ByteString using toByteArray().

[joffrey-bion]

You're calling collect in the current coroutine, so the code will stop there and collect indefinitely without ever reaching sendBinary. For testing purposes like this, you might want to launch a separate coroutine to do the collection of incoming frames:

launch {
    webSocketChannel.incomingFrames.collect {
        if (value is WebSocketFrame.Binary) {
           val v: ByteArray = value.bytes.toByteArray()
           decode(v)
        }
    }
}
webSocketChannel.sendBinary(ByteString(byteArray))

If you're not familiar with coroutines and flow, I suggest you get accustomed to them by reading some coroutine-specific material. The docs of Krossbow assume prior knowledge of coroutines, so there might be jargon or hidden assumptions here and there.

[joffrey-bion]

No. I don't need access to fragments. I need a complete answer.

Then you're good. The ByteString you get as the bytes of the frame will be the complete aggregated message.

[lemkoleg]

I forgot to describe in this pseudocode that the send call is called from

fun someFun (byteArray: ByteArray){
  CoroutineScope(Dispatchers.Default).launch {
      webSocketChannel.sendBinary(ByteString(byteArray))
  }
}

[lemkoleg]

I think I found what the problem is.

[joffrey-bion]

I forgot to describe in this pseudocode that the send call is called from

If someFun is still called like in your example after the collect that is not done in a separate coroutine, the problem still stands

[lemkoleg]

No, no. I definitely call the send data. I see the call through the logs. Now I check if I am trying to send data before the connection is complete, because the connection is started by a separate thread. Tell me, does the WebSocketConnection.canSend variable work correctly?

[joffrey-bion]

As described in the KDoc of WebSocketConnection.canSend, it's a bit unreliable. You can only be sure that false means it will fail, but true doesn't really mean it will succeed. I would be wary about using it, to be frank.

[lemkoleg]

It is enough for me to be sure that this is a false.

[joffrey-bion]

Oh by the way, if you have a WebSocketConnection at all, it is guaranteed that the connection is established already 😉 So if you were using canSend for this, you don't need to. It's more about tracking when the connection is dead afterwards.

[lemkoleg]

I am facing a problem that I can't create an instance of a class.
I don't understand anything. I'm trying to intercept the reason for the coroutine's termination. But there are no errors.

try {
    val webSocketChannel_ = KtorWebSocketClient()
} catch (e: CancellationException){
    Log.d("AAA", "CancellationException")  // Log is empty
} catch (e: Exception) {
  Log.d("AAA", e.stackTraceToString())     // Log is empty
}
 // This code is not called. The coroutine simply terminates without any errors.
 Log.d("AAA", "setConn start")
 val webSocketChannel = webSocketChannel_!!.connect(url = url)

[joffrey-bion]

Did you eventually figure out why you didn't have logs for this? Is this because of the debug level that maybe wasn't enabled?

[lemkoleg]

No. It's because the coroutine was crashing. And since I used to create it SupervisorJob(),
she crashed silently, without disturbing her parents' coroutine. :)

[lemkoleg]

java.lang.ExceptionInInitializerError
at org.hildan.krossbow.websocket.ktor.KtorWebSocketClient.(KtorWebSocketClient.kt:20)
at p_jsocket.KrosbowConnection$setConn$2.invokeSuspend(KroosbowConnection.kt:119)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:102)
at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:589)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:816)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:720)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:707)
Suppressed: kotlinx.coroutines.internal.DiagnosticCoroutineContextException: [StandaloneCoroutine{Cancelling}@6cadd1e, Dispatchers.Default]
Caused by: java.lang.IllegalStateException: Failed to find HTTP client engine implementation in the classpath: consider adding client engine dependency. See https://ktor.io/docs/http-client-engines.html
at io.ktor.client.HttpClientJvmKt.(HttpClientJvm.kt:43)
... 8 more

[lemkoleg]

This problem was solved by adding dependencies for each platform.
https://ktor.io/docs/client-engines.html

[lemkoleg]

I have to add something to build.gredl besides?

implementation("org.hildan.krossbow:krossbow-websocket-ktor:7.0.0")

[lemkoleg]

https://ktor.io/docs/client-engines.html

[lemkoleg]

org.hildan.krossbow.websocket.WebSocketConnectionException: Couldn't connect to web socket at ws://macbook:22237 (java.lang.IllegalArgumentException: Engine doesn't support WebSocketCapability)
at org.hildan.krossbow.websocket.ktor.KtorWebSocketClient.connect(KtorWebSocketClient.kt:48)
at org.hildan.krossbow.websocket.ktor.KtorWebSocketClient$connect$1.invokeSuspend(Unknown Source:15)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:589)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:816)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:720)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:707)
 Caused by: java.lang.IllegalArgumentException: Engine doesn't support WebSocketCapability
at io.ktor.client.engine.HttpClientEngine$DefaultImpls.checkExtensions(HttpClientEngine.kt:105)
at io.ktor.client.engine.HttpClientEngine$DefaultImpls.access$checkExtensions(HttpClientEngine.kt:24)
at io.ktor.client.engine.HttpClientEngine$install$1.invokeSuspend(HttpClientEngine.kt:68)
at io.ktor.client.engine.HttpClientEngine$install$1.invoke(Unknown Source:15)
at io.ktor.client.engine.HttpClientEngine$install$1.invoke(Unknown Source:4)
at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:131)
at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:89)
at io.ktor.util.pipeline.SuspendFunctionGun.execute$ktor_utils(SuspendFunctionGun.kt:109)
at io.ktor.util.pipeline.Pipeline.execute(Pipeline.kt:77)
at io.ktor.client.plugins.HttpSend$DefaultSender.execute(HttpSend.kt:138)
at io.ktor.client.plugins.HttpRedirect$Plugin$install$1.invokeSuspend(HttpRedirect.kt:64)
at io.ktor.client.plugins.HttpRedirect$Plugin$install$1.invoke(Unknown Source:15)
at io.ktor.client.plugins.HttpRedirect$Plugin$install$1.invoke(Unknown Source:6)
at io.ktor.client.plugins.HttpSend$InterceptedSender.execute(HttpSend.kt:116)
at io.ktor.client.plugins.HttpCallValidator$Companion$install$3.invokeSuspend(HttpCallValidator.kt:151)
at io.ktor.client.plugins.HttpCallValidator$Companion$install$3.invoke(Unknown Source:13)
at io.ktor.client.plugins.HttpCallValidator$Companion$install$3.invoke(Unknown Source:6)
at io.ktor.client.plugins.HttpSend$InterceptedSender.execute(HttpSend.kt:116)
at io.ktor.client.plugins.HttpSend$Plugin$install$1.invokeSuspend(HttpSend.kt:104)
at io.ktor.client.plugins.HttpSend$Plugin$install$1.invoke(Unknown Source:15)
at io.ktor.client.plugins.HttpSend$Plugin$install$1.invoke(Unknown Source:4)
at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:131)
at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:89)
at io.ktor.util.pipeline.SuspendFunctionGun.proceedWith(SuspendFunctionGun.kt:99)
at io.ktor.client.plugins.websocket.WebSockets$Plugin$install$1.invokeSuspend(WebSockets.kt:169)
at io.ktor.client.plugins.websocket.WebSockets$Plugin$install$1.invoke(Unknown Source:13)
at io.ktor.client.plugins.websocket.WebSockets$Plugin$install$1.invoke(Unknown Source:4)
at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:131)
at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:89)
at io.ktor.util.pipeline.SuspendFunctionGun.proceedWith(SuspendFunctionGun.kt:99)
at io.ktor.client.plugins.HttpCallValidator$Companion$install$1.invokeSuspend(HttpCallValidator.kt:130)
at io.ktor.client.plugins.HttpCallValidator$Companion$install$1.invoke(Unknown Source:13)
at io.ktor.client.plugins.HttpCallValidator$Companion$install$1.invoke(Unknown Source:4)
at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:131)
at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:89)

[joffrey-bion]

Engine doesn't support WebSocketCapability

You'll need to pick a Ktor engine that supports web sockets: https://ktor.io/docs/client-engines.html#limitations

[lemkoleg]

That's it! It worked! So the result is this:
The whole problem was in the initialization Instance KtorWebSocketClient().
Instance KtorWebSocketClient() requires additional library connections ktor.
( https://ktor.io/docs/client-engines.html )
It is necessary to pay attention that for the Android target you need to connect the library
"io.ktor:ktor-client-okhttp".

Thanks for your help

[joffrey-bion]

Yes, this is described here: https://joffrey-bion.github.io/krossbow/websocket/ktor/#dependency-information

Sorry if that wasn't clear.

[joffrey-bion]

@lemkoleg I'm curious, by the way. Did you follow this page of the doc and missed the end? Or did you not find this page in the first place? It will give me information as to what to put first in the docs. Maybe I should move the dependency section first.

[lemkoleg]

I found the page easily and immediately.
There are no problems here. It's just that I understood the last paragraph
so that additional libraries need to be connected if you use your library directly
(that is, for STOMP). Since I was only interested in the cross-platform WebSocket itself, I ignored it.
It seems to me that there is a lack of indication of the NEED to connect dependencies,
and to demonstrate an example.

[joffrey-bion]

Ok I see, thanks. By the way, if you're only interested in a cross-platform web socket. You could also use Ktor directly without Krossbow at all. Krossbow would just bring an abstraction on top of Ktor that you might not need.

[lemkoleg]

Ok I see, thanks. By the way, if you're only interested in a cross-platform web socket. You could also use Ktor directly without Krossbow at all. Krossbow would just bring an abstraction on top of Ktor that you might not need.

I looked closely at the ktor. But I was confused by what was initialized HttpClient

[lemkoleg]

Thank you for such responsiveness