HttpClient(CIO) {

    install(WebSockets) {
        contentConverter = KotlinxWebsocketSerializationConverter(json)
        pingIntervalMillis = 15000
    }

    install(HttpRequestRetry) {
        retryOnServerErrors(maxRetries = 5)
        delayMillis {
            TODO("handle it here")
            5000
        }
    }
}.webSocket(<url>) { /* TODO */ }

https://ktor.io/docs/client-request-retry.html