Please provide a sample implementation for KMM

[vbanavath]

Hi @joffrey-bion
I am trying to implement the Stomp client web socket utilising krossbow in KMM so that it can work on both iOS and Android
I have gone through the documentation but couldn't get much details like there is no sample implementation or some thing that i can refere for the sample implementation

i have implemented the following thing in the KMM and trying to access it from iOSMainApp

private val httpClient = HttpClient {
        install(WebSockets)
    }
    private val wsClient = KtorWebSocketClient(httpClient)
    private val stompClient = StompClient(wsClient)

    suspend fun connect() {
        val stompSession = stompClient.connect(url = baseUrl, customStompConnectHeaders = headers)
        stompSession.sendText(destination = destination, body = tripDetailsRequest.toString())
        val subscription = stompSession.subscribeText(destination = subscribe)
        subscription.collect {
            println("Received message: $it")
        }
    }

but am not able to establish the connection and getting following error

Uncaught Kotlin exception: org.hildan.krossbow.websocket.WebSocketConnectionException: Couldn't connect to web socket at https://abcd.com/websocketApp/websocket (io.ktor.client.call.NoTransformationFoundException: Expected response body of the type 'class io.ktor.client.plugins.websocket.DefaultClientWebSocketSession' but was 'class io.ktor.utils.io.ByteChannelNative'
In response from https://abcd.com/websocketApp/websocket
Response status 400 Bad Request
Response header ContentType: null
Request header Accept: */*

i have added the dependencies as followed in commonMain

implementation("org.hildan.krossbow:krossbow-websocket-ktor:7.0.0")
implementation("org.hildan.krossbow:krossbow-stomp-kxserialization-json:7.0.0")
implementation("io.ktor:ktor-client-cio:2.3.10")
implementation("io.ktor:ktor-client-websockets:2.3.12")

quick and use full response is very much appreciated!
thanks

[joffrey-bion]

Hi! Thanks for reaching out.

Given that you're getting an HTTP 400, it should be a problem in your initial connection request. There is a chance this is due to the https:// scheme. Have you tried using ws:// or wss:// for your URL?

[vbanavath]

Hi! Thanks for the quick response
but our server supports only https endpoint we don't have a support for ws or wss
Interestingly we tried same thing with iOS native sample(https://github.com/Romixery/SwiftStomp) and its working there we passed as the https only
when we try to achieve the same thing in KMM its throwing the above error

[vbanavath]

i have observed that the session here is not considering the passing headers for the initial communication

suspend fun connect(
        url: String,
        login: String? = null,
        passcode: String? = null,
        host: String? = DefaultHost,
        customStompConnectHeaders: Map<String, String> = emptyMap(),
        sessionCoroutineContext: CoroutineContext = EmptyCoroutineContext,
    ): StompSession {
        val session = withTimeoutOrNull(config.connectionTimeout) {
            **val webSocket = webSocketClient.connect(
                url = url,
                protocols = StompVersion.preferredOrder.map { it.wsSubprotocolId },
            )**
            webSocket.stomp(
                config = config,
                host = host,
                login = login,
                passcode = passcode,
                customHeaders = customStompConnectHeaders,
                sessionCoroutineContext = sessionCoroutineContext,
            )
        }
        return session ?: throw ConnectionTimeout(url, config.connectionTimeout)
    }

webSocketClient is only taking the url and protocols not the passing headers
can we overrode this webSocketClient.connect

[joffrey-bion]

customStompConnectHeaders are headers at the stomp protocol level (they are sent in the STOMP frame, not in the HTTP handshake). If you want to customize the handshake, you can make the handshake separately first, and then use the .stomp() extension function. See the documentation here:
https://joffrey-bion.github.io/krossbow/stomp/advanced-features/#using-custom-headers-in-the-web-socket-handshake

[vbanavath]

we have included map of following headers `"Upgrade" to "websocket","Connection" to "upgrade", along with required one in the but the server says the following error
2024-09-05 11:21:27.370 ERROR [CONNECTED_ORCHESTRATION,dfb858ec6edc18f1,dfb858ec6edc18f1,true] 1 --- [o-1414-exec-222] o.s.w.s.s.s.DefaultHandshakeHandler : Handshake failed due to invalid Upgrade header: null

failed with exception: io.ktor.http.UnsafeHeaderException: Header(s) [Upgrade] are controlled by the engine and cannot be set explicitly

[joffrey-bion]

Yes, you should only set your additional custom headers for the handshake, not the standard websocket handshake headers, as these are taken care of by the websocket implementations. What custom headers did you try to send? Does your server expect some extra headers? If not, there should be no need to customize that.

Another option for getting a 400 could be that your server is expecting the SockJS protocol, but you're connecting using regular websocket protocol. Could you check that? If your spring server has SockJS enabled, you might want to remove that.