diff --git a/.gitignore b/.gitignore
index 0aa06ef89..36975262d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 build
 .gradle
+.gradletasknamecache
 .idea/*
 !.idea/runConfigurations
 !.idea/runConfigurations/*
diff --git a/build.gradle b/build.gradle
index 72e909f65..1aa1438ac 100644
--- a/build.gradle
+++ b/build.gradle
@@ -42,7 +42,10 @@ def projectNeedsPlatform(project, platform) {
     def hasDarwin = files.any { it.name == "darwin" }
 
     if (hasPosix && hasDarwin) return false
-    if (!hasDarwin && platform == "darwin") return false
+
+    if (hasPosix && platform == "darwin") return false
+    if (hasDarwin && platform == "posix") return false
+    if (!hasPosix && !hasDarwin && platform == "darwin") return false
 
     return files.any { it.name == "common" || it.name == platform }
 }
diff --git a/gradle.properties b/gradle.properties
index 399ea1ec9..8385e6e16 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -3,7 +3,7 @@ kotlin.code.style=official
 
 # config
 version=1.2.0-SNAPSHOT
-kotlin.incremental.js=true
+kotlin.incremental.js=false
 kotlin.incremental.multiplatform=true
 
 # gradle
diff --git a/gradle/js.gradle b/gradle/js.gradle
index 4f2c9ba5d..2e2253227 100644
--- a/gradle/js.gradle
+++ b/gradle/js.gradle
@@ -90,6 +90,9 @@ prepareMocha.doLast {
         <script src="$libraryPath/ktor-client.js"></script>
         <script src="$libraryPath/ktor-client-json.js"></script>
         <script src="$libraryPath/ktor-client-auth-basic.js"></script>
+        <script src="$libraryPath/ktor-client-tests-dispatcher.js"></script>
+        <script src="$libraryPath/ktor-client-tests.js"></script>
+        <script src="$libraryPath/ktor-client-websocket.js"></script>
         <script src="$compileTestKotlinJs.outputFile"></script>
         <script>mocha.run();</script>
         </body>
diff --git a/gradle/posix.gradle b/gradle/posix.gradle
index 783c9a306..3d4cfc8ca 100644
--- a/gradle/posix.gradle
+++ b/gradle/posix.gradle
@@ -33,9 +33,18 @@ kotlin {
             configure([iosArm32Main, iosArm64Main, iosX64Main, macosX64Main, linuxX64Main, mingwX64Main]) {
                 dependsOn posixMain
             }
+
             configure([iosArm32Test, iosArm64Test, iosX64Test, macosX64Test, linuxX64Test, mingwX64Test]) {
                 dependsOn posixTest
             }
+
+            iosArm32Test.dependsOn iosArm32Main
+            iosArm64Test.dependsOn iosArm64Main
+            iosX64Test.dependsOn iosX64Main
+            linuxX64Test.dependsOn linuxX64Main
+            macosX64Test.dependsOn macosX64Main
+            iosX64Test.dependsOn iosX64Main
+            mingwX64Test.dependsOn mingwX64Main
         }
     }
 }
diff --git a/ktor-client/build.gradle b/ktor-client/build.gradle
index e704dcecb..08c592191 100644
--- a/ktor-client/build.gradle
+++ b/ktor-client/build.gradle
@@ -1,3 +1,4 @@
+
 kotlin.sourceSets.commonMain.dependencies {
     api project(':ktor-client:ktor-client-core')
 }
diff --git a/ktor-client/ktor-client-cio/build.gradle b/ktor-client/ktor-client-cio/build.gradle
index 8b991afd3..d31f56ea9 100644
--- a/ktor-client/ktor-client-cio/build.gradle
+++ b/ktor-client/ktor-client-cio/build.gradle
@@ -5,6 +5,7 @@ kotlin.sourceSets {
         api project(':ktor-client:ktor-client-core')
         api project(':ktor-http:ktor-http-cio')
         api project(':ktor-network:ktor-network-tls')
+        api project(':ktor-client:ktor-client-features:ktor-client-websocket')
     }
     jvmTest.dependencies {
         api project(':ktor-client:ktor-client-tests')
diff --git a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/CIOEngine.kt b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/CIOEngine.kt
index 0e59125ee..7306d7e14 100644
--- a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/CIOEngine.kt
+++ b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/CIOEngine.kt
@@ -2,7 +2,9 @@ package io.ktor.client.engine.cio
 
 import io.ktor.client.call.*
 import io.ktor.client.engine.*
+import io.ktor.client.features.websocket.*
 import io.ktor.client.request.*
+import io.ktor.client.response.*
 import io.ktor.http.*
 import io.ktor.network.selector.*
 import kotlinx.coroutines.*
@@ -11,7 +13,7 @@ import java.io.*
 import java.util.concurrent.*
 import java.util.concurrent.atomic.*
 
-internal class CIOEngine(override val config: CIOEngineConfig) : HttpClientJvmEngine("ktor-cio") {
+internal class CIOEngine(override val config: CIOEngineConfig) : HttpClientJvmEngine("ktor-cio"), WebSocketEngine {
     private val endpoints = ConcurrentHashMap<String, Endpoint>()
 
     @UseExperimental(InternalCoroutinesApi::class)
@@ -29,7 +31,12 @@ internal class CIOEngine(override val config: CIOEngineConfig) : HttpClientJvmEn
         return@withContext HttpEngineCall(request, response)
     }
 
-    private suspend fun executeRequest(request: DefaultHttpRequest): CIOHttpResponse {
+    override suspend fun execute(request: HttpRequest): WebSocketResponse {
+        val response = executeRequest(request)
+        return response as WebSocketResponse
+    }
+
+    private suspend fun executeRequest(request: HttpRequest): HttpResponse {
         while (true) {
             if (closed.get()) throw ClientClosedException()
 
diff --git a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/CIOHttpResponse.kt b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/CIOHttpResponse.kt
index 5bb11c42a..a81908242 100644
--- a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/CIOHttpResponse.kt
+++ b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/CIOHttpResponse.kt
@@ -11,9 +11,10 @@ import kotlin.coroutines.*
 
 internal class CIOHttpResponse(
     request: HttpRequest,
+    override val headers: Headers,
     override val requestTime: GMTDate,
     override val content: ByteReadChannel,
-    private val response: Response,
+    response: Response,
     override val coroutineContext: CoroutineContext
 ) : HttpResponse {
 
@@ -21,14 +22,7 @@ internal class CIOHttpResponse(
 
     override val status: HttpStatusCode = HttpStatusCode(response.status, response.statusText.toString())
 
-    override val version: HttpProtocolVersion = HttpProtocolVersion.HTTP_1_1
-
-    override val headers: Headers = Headers.build {
-        val origin = CIOHeaders(response.headers)
-        origin.names().forEach {
-            appendAll(it, origin.getAll(it))
-        }
-    }
+    override val version: HttpProtocolVersion = HttpProtocolVersion.parse(response.version)
 
     override val responseTime: GMTDate = GMTDate()
 
diff --git a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/ConnectionFactory.kt b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/ConnectionFactory.kt
index 489601d48..6445afd4b 100644
--- a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/ConnectionFactory.kt
+++ b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/ConnectionFactory.kt
@@ -6,17 +6,20 @@ import io.ktor.network.sockets.*
 import io.ktor.network.sockets.Socket
 import java.net.*
 
-internal class ConnectionFactory(private val selector: SelectorManager, maxConnectionsCount: Int) {
+internal class ConnectionFactory(
+    private val selector: SelectorManager,
+    maxConnectionsCount: Int
+) {
     private val semaphore = Semaphore(maxConnectionsCount)
 
     suspend fun connect(address: InetSocketAddress): Socket {
         semaphore.enter()
         return try {
             aSocket(selector).tcpNoDelay().tcp().connect(address)
-        } catch (t: Throwable) {
+        } catch (cause: Throwable) {
             // a failure or cancellation
             semaphore.leave()
-            throw t
+            throw cause
         }
     }
 
diff --git a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/ConnectionPipeline.kt b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/ConnectionPipeline.kt
index 995f699f7..f20b66e82 100644
--- a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/ConnectionPipeline.kt
+++ b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/ConnectionPipeline.kt
@@ -76,6 +76,11 @@ internal class ConnectionPipeline(
                     val transferEncoding = rawResponse.headers[HttpHeaders.TransferEncoding]
                     val chunked = transferEncoding == "chunked"
                     val connectionType = ConnectionOptions.parse(rawResponse.headers[HttpHeaders.Connection])
+                    val headers = CIOHeaders(rawResponse.headers)
+
+                    callContext[Job]?.invokeOnCompletion {
+                        rawResponse.release()
+                    }
 
                     shouldClose = (connectionType == ConnectionOptions.Close)
 
@@ -90,7 +95,7 @@ internal class ConnectionPipeline(
                     } else ByteReadChannel.Empty
 
                     val response = CIOHttpResponse(
-                        task.request, requestTime,
+                        task.request, headers, requestTime,
                         body,
                         rawResponse,
                         coroutineContext = callContext
@@ -99,19 +104,13 @@ internal class ConnectionPipeline(
                     task.response.complete(response)
 
                     responseChannel?.use {
-                        try {
-                            parseHttpBody(
-                                contentLength,
-                                transferEncoding,
-                                connectionType,
-                                networkInput,
-                                this
-                            )
-                        } finally {
-                            callContext[Job]?.invokeOnCompletion {
-                                rawResponse.release()
-                            }
-                        }
+                        parseHttpBody(
+                            contentLength,
+                            transferEncoding,
+                            connectionType,
+                            networkInput,
+                            this
+                        )
                     }
 
                     skipTask?.join()
diff --git a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/Endpoint.kt b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/Endpoint.kt
index 68fa08972..baf7dfbca 100644
--- a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/Endpoint.kt
+++ b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/Endpoint.kt
@@ -1,19 +1,22 @@
 package io.ktor.client.engine.cio
 
+import io.ktor.client.features.websocket.*
 import io.ktor.client.request.*
+import io.ktor.client.response.*
 import io.ktor.http.*
 import io.ktor.http.cio.*
+import io.ktor.http.cio.websocket.*
 import io.ktor.network.sockets.*
 import io.ktor.network.sockets.Socket
 import io.ktor.network.tls.*
 import io.ktor.util.*
 import io.ktor.util.date.*
+import kotlinx.atomicfu.*
 import kotlinx.coroutines.*
 import kotlinx.coroutines.channels.*
 import kotlinx.coroutines.io.*
 import java.io.*
 import java.net.*
-import java.util.concurrent.atomic.*
 import kotlin.coroutines.*
 
 internal class Endpoint(
@@ -25,14 +28,13 @@ internal class Endpoint(
     override val coroutineContext: CoroutineContext,
     private val onDone: () -> Unit
 ) : CoroutineScope, Closeable {
+    private val address = InetSocketAddress(host, port)
+
+    private val connections: AtomicInt = atomic(0)
     private val tasks: Channel<RequestTask> = Channel(Channel.UNLIMITED)
     private val deliveryPoint: Channel<RequestTask> = Channel()
-    private val maxEndpointIdleTime = 2 * config.endpoint.connectTimeout
 
-    @Volatile
-    private var connectionsHolder: Int = 0
-
-    private val address = InetSocketAddress(host, port)
+    private val maxEndpointIdleTime: Long = 2 * config.endpoint.connectTimeout
 
     private val postman = launch(start = CoroutineStart.LAZY) {
         try {
@@ -64,8 +66,8 @@ internal class Endpoint(
         }
     }
 
-    suspend fun execute(request: DefaultHttpRequest, callContext: CoroutineContext): CIOHttpResponse {
-        val result = CompletableDeferred<CIOHttpResponse>(parent = callContext[Job])
+    suspend fun execute(request: HttpRequest, callContext: CoroutineContext): HttpResponse {
+        val result = CompletableDeferred<HttpResponse>(parent = callContext[Job])
         val task = RequestTask(request, result, callContext)
         tasks.offer(task)
         return result.await()
@@ -74,7 +76,7 @@ internal class Endpoint(
     private suspend fun makePipelineRequest(task: RequestTask) {
         if (deliveryPoint.offer(task)) return
 
-        val connections = Connections.get(this@Endpoint)
+        val connections = connections.value
         if (connections < config.endpoint.maxConnectionsPerRoute) {
             try {
                 createPipeline()
@@ -114,18 +116,20 @@ internal class Endpoint(
             val contentLength = rawResponse.headers[HttpHeaders.ContentLength]?.toString()?.toLong() ?: -1L
             val transferEncoding = rawResponse.headers[HttpHeaders.TransferEncoding]
             val connectionType = ConnectionOptions.parse(rawResponse.headers[HttpHeaders.Connection])
+            val headers = CIOHeaders(rawResponse.headers)
+
+            callContext[Job]!!.invokeOnCompletion {
+                rawResponse.headers.release()
+            }
+
+            if (status == HttpStatusCode.SwitchingProtocols.value) {
+                val session = RawWebSocket(input, output, masking = true, coroutineContext = callContext)
+                response.complete(WebSocketResponse(callContext, requestTime, session))
+                return@launch
+            }
+
 
             val body = when {
-                status == HttpStatusCode.SwitchingProtocols.value -> {
-                    val content = request.content as? ClientUpgradeContent
-                        ?: error("Invalid content type: UpgradeContent required")
-
-                    launch {
-                        content.pipeTo(output)
-                    }.invokeOnCompletion(::closeConnection)
-
-                    input
-                }
                 request.method == HttpMethod.Head -> {
                     closeConnection()
                     ByteReadChannel.Empty
@@ -140,12 +144,12 @@ internal class Endpoint(
                 }
             }
 
-            response.complete(
-                CIOHttpResponse(
-                    request, requestTime, body, rawResponse,
-                    coroutineContext = callContext
-                )
+            val result = CIOHttpResponse(
+                request, headers, requestTime, body, rawResponse,
+                coroutineContext = callContext
             )
+
+            response.complete(result)
         } catch (cause: Throwable) {
             response.completeExceptionally(cause)
         }
@@ -168,7 +172,7 @@ internal class Endpoint(
         val retryAttempts = config.endpoint.connectRetryAttempts
         val connectTimeout = config.endpoint.connectTimeout
 
-        Connections.incrementAndGet(this)
+        connections.incrementAndGet()
 
         try {
             repeat(retryAttempts) {
@@ -187,23 +191,28 @@ internal class Endpoint(
                             address.hostName
                         )
                     }
-                } catch (t: Throwable) {
+                } catch (cause: Throwable) {
+                    try {
+                        connection.close()
+                    } catch (_: Throwable) {
+                    }
+
                     connectionFactory.release()
-                    throw t
+                    throw cause
                 }
             }
         } catch (cause: Throwable) {
-            Connections.decrementAndGet(this)
+            connections.decrementAndGet()
             throw cause
         }
 
-        Connections.decrementAndGet(this)
+        connections.decrementAndGet()
         throw ConnectException()
     }
 
     private fun releaseConnection() {
         connectionFactory.release()
-        Connections.decrementAndGet(this)
+        connections.decrementAndGet()
     }
 
     override fun close() {
@@ -213,12 +222,8 @@ internal class Endpoint(
     init {
         postman.start()
     }
-
-    companion object {
-        private val Connections = AtomicIntegerFieldUpdater
-            .newUpdater(Endpoint::class.java, Endpoint::connectionsHolder.name)
-    }
 }
 
 @KtorExperimentalAPI
+@Suppress("KDocMissingDocumentation")
 class ConnectException : Exception("Connect timed out or retry attempts exceeded")
diff --git a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/EngineTasks.kt b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/EngineTasks.kt
index c20914bdc..ec30d91fe 100644
--- a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/EngineTasks.kt
+++ b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/EngineTasks.kt
@@ -1,14 +1,15 @@
 package io.ktor.client.engine.cio
 
 import io.ktor.client.request.*
+import io.ktor.client.response.*
 import io.ktor.http.*
 import io.ktor.util.date.*
 import kotlinx.coroutines.*
 import kotlin.coroutines.*
 
 internal data class RequestTask(
-    val request: DefaultHttpRequest,
-    val response: CompletableDeferred<CIOHttpResponse>,
+    val request: HttpRequest,
+    val response: CompletableDeferred<HttpResponse>,
     val context: CoroutineContext
 )
 
diff --git a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/utils.kt b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/utils.kt
index 376be75ee..0de42b8b3 100644
--- a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/utils.kt
+++ b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/engine/cio/utils.kt
@@ -9,7 +9,7 @@ import io.ktor.http.content.*
 import kotlinx.coroutines.io.*
 import kotlin.coroutines.*
 
-internal suspend fun DefaultHttpRequest.write(output: ByteWriteChannel, callContext: CoroutineContext) {
+internal suspend fun HttpRequest.write(output: ByteWriteChannel, callContext: CoroutineContext) {
     val builder = RequestResponseBuilder()
 
     val contentLength = headers[HttpHeaders.ContentLength] ?: content.contentLength?.toString()
diff --git a/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/features/websocket/buildersCio.kt b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/features/websocket/buildersCio.kt
new file mode 100644
index 000000000..814ff1e8d
--- /dev/null
+++ b/ktor-client/ktor-client-cio/jvm/src/io/ktor/client/features/websocket/buildersCio.kt
@@ -0,0 +1,49 @@
+package io.ktor.client.features.websocket
+
+import io.ktor.client.*
+import io.ktor.client.request.*
+import io.ktor.http.*
+
+suspend fun HttpClient.webSocketRawSession(
+    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
+    block: HttpRequestBuilder.() -> Unit = {}
+): ClientWebSocketSession = request {
+    this.method = method
+    url("ws", host, port, path)
+    block()
+}
+
+suspend fun HttpClient.webSocketRaw(
+    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
+    request: HttpRequestBuilder.() -> Unit = {}, block: suspend ClientWebSocketSession.() -> Unit
+): Unit {
+    val session = webSocketRawSession(method, host, port, path) {
+        url.protocol = URLProtocol.WS
+        url.port = port
+
+        request()
+    }
+
+    try {
+        session.block()
+    } catch (cause: Throwable) {
+        session.close(cause)
+    } finally {
+        session.close()
+    }
+}
+
+suspend fun HttpClient.wsRaw(
+    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
+    request: HttpRequestBuilder.() -> Unit = {}, block: suspend ClientWebSocketSession.() -> Unit
+): Unit = webSocketRaw(method, host, port, path, request, block)
+
+suspend fun HttpClient.wssRaw(
+    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
+    request: HttpRequestBuilder.() -> Unit = {}, block: suspend ClientWebSocketSession.() -> Unit
+): Unit = webSocketRaw(method, host, port, path, request = {
+    url.protocol = URLProtocol.WSS
+    url.port = port
+
+    request()
+}, block = block)
diff --git a/ktor-client/ktor-client-core/common/src/io/ktor/client/HttpClient.kt b/ktor-client/ktor-client-core/common/src/io/ktor/client/HttpClient.kt
index 1cfe003f2..c183ccf9c 100644
--- a/ktor-client/ktor-client-core/common/src/io/ktor/client/HttpClient.kt
+++ b/ktor-client/ktor-client-core/common/src/io/ktor/client/HttpClient.kt
@@ -52,14 +52,16 @@ fun HttpClient(
  * Asynchronous client to perform HTTP requests.
  *
  * This is a generic implementation that uses a specific engine [HttpClientEngine].
+ * @property engine: [HttpClientEngine] for executing requests.
  */
 class HttpClient(
-    private val engine: HttpClientEngine,
+    @InternalAPI val engine: HttpClientEngine,
     private val userConfig: HttpClientConfig<out HttpClientEngineConfig> = HttpClientConfig()
 ) : CoroutineScope, Closeable {
     private val closed = atomic(false)
 
     override val coroutineContext: CoroutineContext get() = engine.coroutineContext
+
     /**
      * Pipeline used for processing all the requests sent by this client.
      */
diff --git a/ktor-client/ktor-client-core/common/src/io/ktor/client/call/HttpClientCall.kt b/ktor-client/ktor-client-core/common/src/io/ktor/client/call/HttpClientCall.kt
index adfbf9201..44e0a258e 100644
--- a/ktor-client/ktor-client-core/common/src/io/ktor/client/call/HttpClientCall.kt
+++ b/ktor-client/ktor-client-core/common/src/io/ktor/client/call/HttpClientCall.kt
@@ -4,6 +4,7 @@ import io.ktor.client.*
 import io.ktor.client.features.*
 import io.ktor.client.request.*
 import io.ktor.client.response.*
+import io.ktor.util.*
 import kotlinx.atomicfu.*
 import kotlinx.coroutines.*
 import kotlinx.io.core.*
@@ -13,9 +14,9 @@ import kotlin.reflect.*
 /**
  * A class that represents a single pair of [request] and [response] for a specific [HttpClient].
  *
- * [client] - client that executed the call.
+ * @property client: client that executed the call.
  */
-class HttpClientCall internal constructor(
+open class HttpClientCall constructor(
     val client: HttpClient
 ) : CoroutineScope, Closeable {
     private val received = atomic(false)
@@ -23,7 +24,12 @@ class HttpClientCall internal constructor(
     override val coroutineContext: CoroutineContext get() = response.coroutineContext
 
     /**
-     * Represents the [request] sent by the client.
+     * Typed [Attributes] associated to this call serving as a lightweight container.
+     */
+    val attributes: Attributes get() = request.attributes
+
+    /**
+     * Represents the [request] sent by the client
      */
     lateinit var request: HttpRequest
         internal set
@@ -70,6 +76,12 @@ class HttpClientCall internal constructor(
     }
 }
 
+/**
+ * Raw http call produced by engine.
+ *
+ * @property request - executed http request.
+ * @property response - raw http response
+ */
 data class HttpEngineCall(val request: HttpRequest, val response: HttpResponse)
 
 /**
@@ -98,6 +110,7 @@ suspend inline fun <reified T> HttpResponse.receive(): T = call.receive(typeInfo
 /**
  * Exception representing that the response payload has already been received.
  */
+@Suppress("KDocMissingDocumentation")
 class DoubleReceiveException(call: HttpClientCall) : IllegalStateException() {
     override val message: String = "Response already received: $call"
 }
@@ -106,6 +119,7 @@ class DoubleReceiveException(call: HttpClientCall) : IllegalStateException() {
  * Exception representing fail of the response pipeline
  * [cause] contains origin pipeline exception
  */
+@Suppress("KDocMissingDocumentation")
 class ReceivePipelineException(
     val request: HttpClientCall,
     val info: TypeInfo,
@@ -116,6 +130,7 @@ class ReceivePipelineException(
  * Exception representing the no transformation was found.
  * It includes the received type and the expected type as part of the message.
  */
+@Suppress("KDocMissingDocumentation")
 class NoTransformationFoundException(from: KClass<*>, to: KClass<*>) : UnsupportedOperationException() {
     override val message: String? = "No transformation found: $from -> $to"
 }
@@ -125,4 +140,5 @@ class NoTransformationFoundException(from: KClass<*>, to: KClass<*>) : Unsupport
     ReplaceWith("NoTransformationFoundException"),
     DeprecationLevel.ERROR
 )
+@Suppress("KDocMissingDocumentation")
 typealias NoTransformationFound = NoTransformationFoundException
diff --git a/ktor-client/ktor-client-core/common/src/io/ktor/client/call/utils.kt b/ktor-client/ktor-client-core/common/src/io/ktor/client/call/utils.kt
index 05a328c88..0dc543ebf 100644
--- a/ktor-client/ktor-client-core/common/src/io/ktor/client/call/utils.kt
+++ b/ktor-client/ktor-client-core/common/src/io/ktor/client/call/utils.kt
@@ -9,6 +9,10 @@ import io.ktor.http.content.*
 class UnsupportedContentTypeException(content: OutgoingContent) :
     IllegalStateException("Failed to write body: ${content::class}")
 
+class UnsupportedUpgradeProtocolException(
+    url: Url
+) : IllegalArgumentException("Unsupported upgrade protocol exception: $url")
+
 /**
  * Constructs a [HttpClientCall] from this [HttpClient] and
  * with the specified HTTP request [builder].
diff --git a/ktor-client/ktor-client-core/common/src/io/ktor/client/features/HttpSend.kt b/ktor-client/ktor-client-core/common/src/io/ktor/client/features/HttpSend.kt
index 68cbfd266..89b927b1e 100644
--- a/ktor-client/ktor-client-core/common/src/io/ktor/client/features/HttpSend.kt
+++ b/ktor-client/ktor-client-core/common/src/io/ktor/client/features/HttpSend.kt
@@ -61,7 +61,7 @@ class HttpSend(
                 do {
                     callChanged = false
 
-                    passInterceptors@for (interceptor in feature.interceptors) {
+                    passInterceptors@ for (interceptor in feature.interceptors) {
                         val transformed = interceptor(sender, currentCall)
                         if (transformed === currentCall) continue@passInterceptors
 
@@ -77,7 +77,7 @@ class HttpSend(
     }
 
     private class DefaultSender(private val maxSendCount: Int, private val client: HttpClient) : Sender {
-        private var sentCount =  0
+        private var sentCount: Int = 0
 
         override suspend fun execute(requestBuilder: HttpRequestBuilder): HttpClientCall {
             if (sentCount >= maxSendCount) throw SendCountExceedException("Max send count $maxSendCount exceeded")
diff --git a/ktor-client/ktor-client-core/common/src/io/ktor/client/request/Content.kt b/ktor-client/ktor-client-core/common/src/io/ktor/client/request/Content.kt
index 00e1e98e3..5ea8c7a13 100644
--- a/ktor-client/ktor-client-core/common/src/io/ktor/client/request/Content.kt
+++ b/ktor-client/ktor-client-core/common/src/io/ktor/client/request/Content.kt
@@ -5,7 +5,7 @@ import io.ktor.http.*
 import kotlinx.coroutines.io.*
 
 abstract class ClientUpgradeContent : OutgoingContent.NoContent() {
-    private val content: ByteChannel = ByteChannel()
+    private val content: ByteChannel by lazy { ByteChannel() }
 
     val output: ByteWriteChannel get() = content
 
diff --git a/ktor-client/ktor-client-core/common/src/io/ktor/client/request/HttpRequest.kt b/ktor-client/ktor-client-core/common/src/io/ktor/client/request/HttpRequest.kt
index 7a3a0f44b..56516351b 100644
--- a/ktor-client/ktor-client-core/common/src/io/ktor/client/request/HttpRequest.kt
+++ b/ktor-client/ktor-client-core/common/src/io/ktor/client/request/HttpRequest.kt
@@ -32,7 +32,7 @@ interface HttpRequest : HttpMessage, CoroutineScope {
     val url: Url
 
     /**
-     * Typed [Attributes] associated to this request serving as a lightweight container.
+     * Typed [Attributes] associated to this call serving as a lightweight container.
      */
     val attributes: Attributes
 
@@ -44,13 +44,13 @@ interface HttpRequest : HttpMessage, CoroutineScope {
         level = DeprecationLevel.ERROR,
         replaceWith = ReplaceWith("coroutineContext")
     )
-    val executionContext: Job get() = TODO()
+    val executionContext: Job
+        get() = TODO()
 
     /**
      * An [OutgoingContent] representing the request body
      */
     val content: OutgoingContent
-
 }
 
 /**
diff --git a/ktor-client/ktor-client-core/common/src/io/ktor/client/response/HttpResponse.kt b/ktor-client/ktor-client-core/common/src/io/ktor/client/response/HttpResponse.kt
index 9285c1742..a77de6bf8 100644
--- a/ktor-client/ktor-client-core/common/src/io/ktor/client/response/HttpResponse.kt
+++ b/ktor-client/ktor-client-core/common/src/io/ktor/client/response/HttpResponse.kt
@@ -8,7 +8,6 @@ import kotlinx.coroutines.*
 import kotlinx.coroutines.io.*
 import kotlinx.io.charsets.*
 import kotlinx.io.core.*
-import kotlinx.io.core.Closeable
 
 /**
  * A response for [HttpClient], second part of [HttpClientCall].
@@ -49,13 +48,15 @@ interface HttpResponse : HttpMessage, CoroutineScope, Closeable {
         replaceWith = ReplaceWith("coroutineContext"),
         level = DeprecationLevel.ERROR
     )
-    val executionContext: Job get() = coroutineContext[Job]!!
+    val executionContext: Job
+        get() = coroutineContext[Job]!!
 
     /**
      * [ByteReadChannel] with the payload of the response.
      */
     val content: ByteReadChannel
 
+    @Suppress("KDocMissingDocumentation")
     override fun close() {
         @Suppress("UNCHECKED_CAST")
         (coroutineContext[Job] as CompletableDeferred<Unit>).complete(Unit)
diff --git a/ktor-client/ktor-client-core/posix/src/io/ktor/client/HttpClient.kt b/ktor-client/ktor-client-core/posix/src/io/ktor/client/HttpClient.kt
index 946ca2e45..5c47b3daa 100644
--- a/ktor-client/ktor-client-core/posix/src/io/ktor/client/HttpClient.kt
+++ b/ktor-client/ktor-client-core/posix/src/io/ktor/client/HttpClient.kt
@@ -11,7 +11,6 @@ import io.ktor.client.engine.*
 @HttpClientDsl
 actual fun HttpClient(
     block: HttpClientConfig<*>.() -> Unit
-): HttpClient = engines.firstOrNull()?.let { HttpClient(it, block) }
-    ?: error(
-        "Failed to find HttpClientEngineContainer. Consider adding [HttpClientEngine] implementation in dependencies."
-    )
+): HttpClient = engines.firstOrNull()?.let { HttpClient(it, block) } ?: error(
+    "Failed to find HttpClientEngineContainer. Consider adding [HttpClientEngine] implementation in dependencies."
+)
diff --git a/ktor-client/ktor-client-core/posix/src/io/ktor/client/engine/Loader.kt b/ktor-client/ktor-client-core/posix/src/io/ktor/client/engine/Loader.kt
index 1c43b51d6..dd5aad34a 100644
--- a/ktor-client/ktor-client-core/posix/src/io/ktor/client/engine/Loader.kt
+++ b/ktor-client/ktor-client-core/posix/src/io/ktor/client/engine/Loader.kt
@@ -1,5 +1,6 @@
 package io.ktor.client.engine
 
+import kotlin.native.concurrent.*
 import io.ktor.util.*
 
 @InternalAPI
diff --git a/ktor-client/ktor-client-curl/posix/src/io/ktor/client/engine/curl/Curl.kt b/ktor-client/ktor-client-curl/posix/src/io/ktor/client/engine/curl/Curl.kt
index 12a6af4a4..b0501f9f1 100644
--- a/ktor-client/ktor-client-curl/posix/src/io/ktor/client/engine/curl/Curl.kt
+++ b/ktor-client/ktor-client-curl/posix/src/io/ktor/client/engine/curl/Curl.kt
@@ -1,5 +1,6 @@
 package io.ktor.client.engine.curl
 
+import kotlin.native.concurrent.*
 import io.ktor.client.engine.*
 import libcurl.*
 
@@ -14,6 +15,10 @@ private val curlGlobalInitReturnCode = curl_global_init(CURL_GLOBAL_ALL)
 @ThreadLocal
 private val initHook = Curl
 
+/**
+ * [HttpClientEngineFactory] using a curl library in implementation
+ * with the the associated configuration [HttpClientEngineConfig].
+ */
 object Curl : HttpClientEngineFactory<HttpClientEngineConfig> {
 
     init {
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/build.gradle b/ktor-client/ktor-client-features/ktor-client-websocket/build.gradle
index 015e9bb40..3300a4349 100644
--- a/ktor-client/ktor-client-features/ktor-client-websocket/build.gradle
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/build.gradle
@@ -1,12 +1,16 @@
 description = "Ktor websocket support"
 
 kotlin.sourceSets {
-    jvmMain.dependencies {
+    commonMain.dependencies {
         api project(':ktor-client:ktor-client-core')
         api project(':ktor-http:ktor-http-cio')
     }
+    commonTest.dependencies {
+        api project(':ktor-client:ktor-client-tests')
+    }
     jvmTest.dependencies {
         api project(':ktor-client:ktor-client-cio')
+        api project(':ktor-client:ktor-client-okhttp')
         api project(':ktor-features:ktor-websockets')
         api project(':ktor-client:ktor-client-tests')
     }
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/ClientSessions.kt b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/ClientSessions.kt
similarity index 66%
rename from ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/ClientSessions.kt
rename to ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/ClientSessions.kt
index aaa092686..fef7d4495 100644
--- a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/ClientSessions.kt
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/ClientSessions.kt
@@ -19,8 +19,8 @@ interface ClientWebSocketSession : WebSocketSession {
 class DefaultClientWebSocketSession(
     override val call: HttpClientCall,
     delegate: DefaultWebSocketSession
-) : ClientWebSocketSession, DefaultWebSocketSession by delegate {
-    init {
-        masking = true
-    }
-}
+) : ClientWebSocketSession, DefaultWebSocketSession by delegate
+
+internal class DelegatingClientWebSocketSession(
+    override val call: HttpClientCall, session: WebSocketSession
+) : ClientWebSocketSession, WebSocketSession by session
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketCall.kt b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketCall.kt
new file mode 100644
index 000000000..43823dc90
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketCall.kt
@@ -0,0 +1,6 @@
+package io.ktor.client.features.websocket
+
+import io.ktor.client.*
+import io.ktor.client.call.*
+
+internal class WebSocketCall(client: HttpClient) : HttpClientCall(client)
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/WebSocketContent.kt b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketContent.kt
similarity index 73%
rename from ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/WebSocketContent.kt
rename to ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketContent.kt
index 56b2e4477..65f61a54c 100644
--- a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/WebSocketContent.kt
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketContent.kt
@@ -4,17 +4,14 @@ import io.ktor.client.request.*
 import io.ktor.http.*
 import io.ktor.http.websocket.*
 import io.ktor.util.*
-import java.util.*
 
 private const val WEBSOCKET_VERSION = "13"
 private const val NONCE_SIZE = 16
 
-class WebSocketContent: ClientUpgradeContent() {
-
+internal class WebSocketContent : ClientUpgradeContent() {
     private val nonce: String = buildString {
-        val bytes = ByteArray(NONCE_SIZE)
-        random.nextBytes(bytes)
-        append(encodeBase64(bytes))
+        val nonce = generateNonce(NONCE_SIZE)
+        append(nonce.encodeBase64())
     }
 
     override val headers: Headers = HeadersBuilder().apply {
@@ -27,15 +24,11 @@ class WebSocketContent: ClientUpgradeContent() {
 
     override fun verify(headers: Headers) {
         val serverAccept = headers[HttpHeaders.SecWebSocketAccept]
-                ?: error("Server should specify header ${HttpHeaders.SecWebSocketAccept}")
+            ?: error("Server should specify header ${HttpHeaders.SecWebSocketAccept}")
 
         val expectedAccept = websocketServerAccept(nonce)
         check(expectedAccept == serverAccept) {
             "Failed to verify server accept header. Expected: $expectedAccept, received: $serverAccept"
         }
     }
-
-    companion object {
-        private val random = Random()
-    }
 }
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketEngine.kt b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketEngine.kt
new file mode 100644
index 000000000..ee1bcbd5f
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketEngine.kt
@@ -0,0 +1,17 @@
+package io.ktor.client.features.websocket
+
+import io.ktor.client.request.*
+import kotlinx.coroutines.*
+
+internal expect fun findWebSocketEngine(): WebSocketEngine
+
+/**
+ * Client engine implementing WebSocket protocol.
+ * RFC: https://tools.ietf.org/html/rfc6455
+ */
+interface WebSocketEngine : CoroutineScope {
+    /**
+     * Execute WebSocket protocol [request].
+     */
+    suspend fun execute(request: HttpRequest): WebSocketResponse
+}
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketResponse.kt b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketResponse.kt
new file mode 100644
index 000000000..06c969bec
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSocketResponse.kt
@@ -0,0 +1,34 @@
+package io.ktor.client.features.websocket
+
+import io.ktor.client.call.*
+import io.ktor.client.response.*
+import io.ktor.http.*
+import io.ktor.http.cio.websocket.*
+import io.ktor.util.date.*
+import kotlinx.coroutines.io.*
+import kotlin.coroutines.*
+
+/**
+ * Response produced by [WebSocketEngine].
+ *
+ * @property session - connection [WebSocketSession].
+ */
+class WebSocketResponse(
+    override val coroutineContext: CoroutineContext,
+    override val requestTime: GMTDate,
+    val session: WebSocketSession,
+    override val headers: Headers = Headers.Empty,
+    override val status: HttpStatusCode = HttpStatusCode.SwitchingProtocols,
+    override val version: HttpProtocolVersion = HttpProtocolVersion.HTTP_1_1
+) : HttpResponse {
+
+    override lateinit var call: HttpClientCall
+        internal set
+
+    override val responseTime: GMTDate = GMTDate()
+
+    override val content: ByteReadChannel
+        get() = throw WebSocketException(
+            "Bytes from [content] is not available in [WebSocketResponse]. Consider using [session] instead."
+        )
+}
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSockets.kt b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSockets.kt
new file mode 100644
index 000000000..59ac22388
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/WebSockets.kt
@@ -0,0 +1,93 @@
+package io.ktor.client.features.websocket
+
+
+import io.ktor.client.*
+import io.ktor.client.features.*
+import io.ktor.client.request.*
+import io.ktor.client.response.*
+import io.ktor.http.*
+import io.ktor.http.cio.websocket.*
+import io.ktor.util.*
+import io.ktor.util.pipeline.*
+
+/**
+ * Client WebSocket feature.
+ *
+ * @property pingInterval - interval between [FrameType.PING] messages.
+ * @property maxFrameSize - max size of single websocket frame.
+ */
+@KtorExperimentalAPI
+@UseExperimental(WebSocketInternalAPI::class)
+class WebSockets(
+    val pingInterval: Long = -1L,
+    val maxFrameSize: Long = Int.MAX_VALUE.toLong()
+) {
+    internal val engine: WebSocketEngine by lazy { findWebSocketEngine() }
+
+    private suspend fun execute(client: HttpClient, content: HttpRequestData): WebSocketCall {
+        val clientEngine = client.engine
+        val currentEngine = if (clientEngine is WebSocketEngine) clientEngine else engine
+
+        val result = WebSocketCall(client)
+        val request = DefaultHttpRequest(result, content)
+
+        val response = currentEngine.execute(request).apply {
+            call = result
+        }
+
+        result.response = response
+        return result
+    }
+
+    @Suppress("KDocMissingDocumentation")
+    companion object Feature : HttpClientFeature<Unit, WebSockets> {
+        override val key: AttributeKey<WebSockets> = AttributeKey("Websocket")
+
+        override fun prepare(block: Unit.() -> Unit): WebSockets = WebSockets()
+
+        override fun install(feature: WebSockets, scope: HttpClient) {
+            scope.requestPipeline.intercept(HttpRequestPipeline.Render) { _ ->
+                if (!context.url.protocol.isWebsocket()) return@intercept
+
+                proceedWith(WebSocketContent())
+            }
+
+            val WebSocket = PipelinePhase("WebSocket")
+            scope.sendPipeline.insertPhaseBefore(HttpSendPipeline.Engine, WebSocket)
+            scope.sendPipeline.intercept(WebSocket) { content ->
+                if (content !is WebSocketContent) return@intercept
+                finish()
+
+                context.body = content
+                val requestData = context.build()
+
+                proceedWith(feature.execute(scope, requestData))
+            }
+
+            scope.responsePipeline.intercept(HttpResponsePipeline.Transform) { (info, response) ->
+                if (response !is WebSocketResponse) return@intercept
+
+                with(feature) {
+                    val session = response.session
+                    val expected = info.type
+
+                    if (expected == DefaultClientWebSocketSession::class) {
+                        val clientSession = DefaultClientWebSocketSession(context, session.asDefault())
+                        proceedWith(HttpResponseContainer(info, clientSession))
+                        return@intercept
+                    }
+
+                    proceedWith(HttpResponseContainer(info, DelegatingClientWebSocketSession(context, session)))
+                }
+            }
+        }
+    }
+
+    private fun WebSocketSession.asDefault(): DefaultWebSocketSession {
+        if (this is DefaultWebSocketSession) return this
+        return DefaultWebSocketSession(this, pingInterval, maxFrameSize)
+    }
+}
+
+@Suppress("KDocMissingDocumentation")
+class WebSocketException(message: String) : IllegalStateException(message)
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/builders.kt b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/builders.kt
new file mode 100644
index 000000000..3b49f99eb
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/common/src/io/ktor/client/features/websocket/builders.kt
@@ -0,0 +1,65 @@
+package io.ktor.client.features.websocket
+
+import io.ktor.client.*
+import io.ktor.client.features.*
+import io.ktor.client.request.*
+import io.ktor.http.*
+import io.ktor.http.cio.websocket.*
+import kotlinx.coroutines.*
+
+/**
+ * Open [DefaultClientWebSocketSession].
+ */
+@UseExperimental(WebSocketInternalAPI::class)
+suspend fun HttpClient.webSocketSession(
+    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
+    block: HttpRequestBuilder.() -> Unit = {}
+): DefaultClientWebSocketSession = request {
+    this.method = method
+    url("ws", host, port, path)
+    block()
+}
+
+/**
+ * Open [block] with [DefaultClientWebSocketSession].
+ */
+suspend fun HttpClient.webSocket(
+    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
+    request: HttpRequestBuilder.() -> Unit = {}, block: suspend DefaultClientWebSocketSession.() -> Unit
+): Unit {
+    val session = webSocketSession(method, host, port, path) {
+        url.protocol = URLProtocol.WS
+        url.port = port
+        request()
+    }
+
+    try {
+        session.block()
+    } catch (cause: Throwable) {
+        session.close(cause)
+        throw cause
+    } finally {
+        session.close(null)
+    }
+}
+
+/**
+ * Open [DefaultClientWebSocketSession].
+ */
+suspend fun HttpClient.ws(
+    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
+    request: HttpRequestBuilder.() -> Unit = {}, block: suspend DefaultClientWebSocketSession.() -> Unit
+): Unit = webSocket(method, host, port, path, request, block)
+
+/**
+ * Open secure [DefaultClientWebSocketSession].
+ */
+suspend fun HttpClient.wss(
+    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
+    request: HttpRequestBuilder.() -> Unit = {}, block: suspend DefaultClientWebSocketSession.() -> Unit
+): Unit = webSocket(method, host, port, path, request = {
+    url.protocol = URLProtocol.WSS
+    url.port = port
+
+    request()
+}, block = block)
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/common/test/WebSocketRemoteTest.kt b/ktor-client/ktor-client-features/ktor-client-websocket/common/test/WebSocketRemoteTest.kt
new file mode 100644
index 000000000..cfdc91dcc
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/common/test/WebSocketRemoteTest.kt
@@ -0,0 +1,59 @@
+package io.ktor.client.features.websocket
+
+import io.ktor.client.tests.utils.*
+import io.ktor.http.cio.websocket.*
+import kotlinx.io.core.*
+import kotlin.test.*
+
+class WebSocketRemoteTest {
+
+    @Test
+    fun testRemotePingPong() = clientsTest {
+        val remote = "echo.websocket.org"
+
+        config {
+            install(WebSockets)
+        }
+
+        test { client ->
+            client.ws(host = remote) {
+                repeat(10) {
+                    ping(it.toString())
+                }
+            }
+        }
+    }
+
+    @Test
+    fun testSecureRemotePingPong() = clientsTest {
+        val remote = "echo.websocket.org"
+
+        config {
+            install(WebSockets)
+        }
+
+        test { client ->
+            client.wss(host = remote) {
+                repeat(10) {
+                    ping(it.toString())
+                }
+            }
+        }
+    }
+
+    private suspend fun WebSocketSession.ping(salt: String) {
+        outgoing.send(Frame.Text("text: $salt"))
+        val frame = incoming.receive()
+        check(frame is Frame.Text)
+
+        assertEquals("text: $salt", frame.readText())
+
+        val data = "text: $salt".toByteArray()
+        outgoing.send(Frame.Binary(true, data))
+        val binaryFrame = incoming.receive()
+        check(binaryFrame is Frame.Binary)
+
+        val buffer = binaryFrame.data
+        assertEquals(data.contentToString(), buffer.contentToString())
+    }
+}
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/js/src/io/ktor/client/features/websocket/JsWebSocketSession.kt b/ktor-client/ktor-client-features/ktor-client-websocket/js/src/io/ktor/client/features/websocket/JsWebSocketSession.kt
new file mode 100644
index 000000000..1ab67f252
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/js/src/io/ktor/client/features/websocket/JsWebSocketSession.kt
@@ -0,0 +1,98 @@
+package io.ktor.client.features.websocket
+
+import io.ktor.http.cio.websocket.*
+import io.ktor.util.*
+import kotlinx.coroutines.*
+import kotlinx.coroutines.channels.*
+import kotlinx.io.core.*
+import org.khronos.webgl.*
+import org.w3c.dom.*
+import kotlin.coroutines.*
+
+internal class JsWebSocketSession(
+    override val coroutineContext: CoroutineContext,
+    private val websocket: WebSocket
+) : DefaultWebSocketSession {
+    private val _closeReason: CompletableDeferred<CloseReason> = CompletableDeferred()
+    private val _incoming: Channel<Frame> = Channel(Channel.UNLIMITED)
+    private val _outgoing: Channel<Frame> = Channel(Channel.UNLIMITED)
+
+    override val incoming: ReceiveChannel<Frame> = _incoming
+    override val outgoing: SendChannel<Frame> = _outgoing
+
+    override val closeReason: Deferred<CloseReason?> = _closeReason
+
+    init {
+        websocket.binaryType = BinaryType.ARRAYBUFFER
+
+        websocket.onmessage = { event ->
+            launch {
+                val data = event.data
+
+                val frame: Frame = when (data) {
+                    is ArrayBuffer -> Frame.Binary(false, Int8Array(data) as ByteArray)
+                    is String -> Frame.Text(event.data as String)
+                    else -> error("Unknown frame type: ${event.type}")
+                }
+
+                _incoming.offer(frame)
+            }
+        }
+
+        websocket.onerror = {
+            _incoming.close(WebSocketException("$it"))
+            _outgoing.cancel()
+        }
+
+        websocket.onclose = {
+            launch {
+                val event = it as CloseEvent
+                _incoming.send(Frame.Close(CloseReason(event.code, event.reason)))
+                _incoming.close()
+
+                _outgoing.cancel()
+            }
+        }
+
+        launch {
+            _outgoing.consumeEach {
+                when (it.frameType) {
+                    FrameType.TEXT -> {
+                        val text = it.data
+                        websocket.send(String(text))
+                    }
+                    FrameType.BINARY -> {
+                        val source = it.data as Int8Array
+                        val frameData = source.buffer.slice(
+                            source.byteOffset, source.byteOffset + source.byteLength
+                        )
+
+                        websocket.send(frameData)
+                    }
+                    FrameType.CLOSE -> {
+                        val data = buildPacket { it.data }
+                        websocket.close(data.readShort(), data.readText())
+                    }
+                }
+            }
+        }
+    }
+
+    override suspend fun flush() {
+    }
+
+    override fun terminate() {
+        _incoming.cancel()
+        _outgoing.cancel()
+        websocket.close()
+    }
+
+    @KtorExperimentalAPI
+    override suspend fun close(cause: Throwable?) {
+        val reason = cause?.let {
+            CloseReason(CloseReason.Codes.UNEXPECTED_CONDITION, cause.message ?: "")
+        } ?: CloseReason(CloseReason.Codes.NORMAL, "OK")
+
+        _incoming.send(Frame.Close(reason))
+    }
+}
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/js/src/io/ktor/client/features/websocket/WebSocketEngineJs.kt b/ktor-client/ktor-client-features/ktor-client-websocket/js/src/io/ktor/client/features/websocket/WebSocketEngineJs.kt
new file mode 100644
index 000000000..280766fdd
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/js/src/io/ktor/client/features/websocket/WebSocketEngineJs.kt
@@ -0,0 +1,34 @@
+package io.ktor.client.features.websocket
+
+import io.ktor.client.request.*
+import io.ktor.util.date.*
+import kotlinx.coroutines.*
+import org.w3c.dom.*
+import kotlin.coroutines.*
+
+internal actual fun findWebSocketEngine(): WebSocketEngine = DefaultJsWebSocketEngine()
+
+internal class DefaultJsWebSocketEngine() : WebSocketEngine {
+    override val coroutineContext: CoroutineContext = Dispatchers.Default
+
+    override suspend fun execute(request: HttpRequest): WebSocketResponse {
+        val requestTime = GMTDate()
+        val callContext = CompletableDeferred<Unit>() + coroutineContext
+
+        val socket = WebSocket(request.url.toString()).apply { await() }
+        val session = JsWebSocketSession(callContext, socket)
+
+        return WebSocketResponse(callContext, requestTime, session)
+    }
+
+    private suspend fun WebSocket.await(): Unit = suspendCancellableCoroutine { continuation ->
+        onopen = {
+            onopen = undefined
+            onerror = undefined
+            continuation.resume(Unit)
+        }
+        onerror = {
+            continuation.resumeWithException(WebSocketException("$it"))
+        }
+    }
+}
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/WebSocketEngineJvm.kt b/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/WebSocketEngineJvm.kt
new file mode 100644
index 000000000..ee9ddffa8
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/WebSocketEngineJvm.kt
@@ -0,0 +1,5 @@
+package io.ktor.client.features.websocket
+
+internal actual fun findWebSocketEngine(): WebSocketEngine = error(
+    "Failed to find WebSocket client engine implementation in the classpath: consider adding WebSocketEngine dependency."
+)
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/WebSockets.kt b/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/WebSockets.kt
deleted file mode 100644
index 6868b6591..000000000
--- a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/WebSockets.kt
+++ /dev/null
@@ -1,65 +0,0 @@
-package io.ktor.client.features.websocket
-
-import io.ktor.client.*
-import io.ktor.client.call.*
-import io.ktor.client.features.*
-import io.ktor.client.request.*
-import io.ktor.client.response.*
-import io.ktor.http.*
-import io.ktor.http.cio.websocket.*
-import io.ktor.util.*
-import kotlinx.coroutines.*
-import kotlinx.io.core.*
-import kotlin.reflect.full.*
-
-/**
- * Client WebSocket feature.
- */
-class WebSockets(
-    val maxFrameSize: Long = Int.MAX_VALUE.toLong()
-) : Closeable {
-
-    @KtorExperimentalAPI
-    val context = CompletableDeferred<Unit>()
-
-    override fun close() {
-        context.complete(Unit)
-    }
-
-    companion object Feature : HttpClientFeature<Unit, WebSockets> {
-        override val key: AttributeKey<WebSockets> = AttributeKey("Websocket")
-
-        override fun prepare(block: Unit.() -> Unit): WebSockets = WebSockets()
-
-        override fun install(feature: WebSockets, scope: HttpClient) {
-            scope.requestPipeline.intercept(HttpRequestPipeline.Render) { _ ->
-                if (!context.url.protocol.isWebsocket()) return@intercept
-                proceedWith(WebSocketContent())
-            }
-
-            scope.responsePipeline.intercept(HttpResponsePipeline.Transform) { (info, response) ->
-                val content = context.request.content
-
-                if (!info.type.isSubclassOf(WebSocketSession::class)
-                    || response !is HttpResponse
-                    || response.status.value != HttpStatusCode.SwitchingProtocols.value
-                    || content !is WebSocketContent
-                ) return@intercept
-
-                content.verify(response.headers)
-
-                val raw = RawWebSocket(
-                    response.content, content.output,
-                    feature.maxFrameSize,
-                    coroutineContext = response.coroutineContext
-                )
-
-                val session = object : ClientWebSocketSession, WebSocketSession by raw {
-                    override val call: HttpClientCall = response.call
-                }
-
-                proceedWith(HttpResponseContainer(info, session))
-            }
-        }
-    }
-}
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/builders.kt b/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/builders.kt
deleted file mode 100644
index 0c4b04186..000000000
--- a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/src/io/ktor/client/features/websocket/builders.kt
+++ /dev/null
@@ -1,102 +0,0 @@
-package io.ktor.client.features.websocket
-
-import io.ktor.client.*
-import io.ktor.client.features.*
-import io.ktor.client.request.*
-import io.ktor.http.*
-import io.ktor.http.cio.websocket.*
-import kotlinx.coroutines.*
-
-suspend fun HttpClient.webSocketRawSession(
-    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
-    block: HttpRequestBuilder.() -> Unit = {}
-): ClientWebSocketSession = request {
-    this.method = method
-    url("ws", host, port, path)
-    block()
-}
-
-@UseExperimental(WebSocketInternalAPI::class)
-suspend fun HttpClient.webSocketSession(
-    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
-    block: HttpRequestBuilder.() -> Unit = {}
-): DefaultClientWebSocketSession {
-    val feature = feature(WebSockets) ?: error("WebSockets feature should be installed")
-    val session = webSocketRawSession(method, host, port, path, block)
-    val origin = DefaultWebSocketSessionImpl(session)
-
-    feature.context.invokeOnCompletion {
-        session.launch { origin.goingAway("Client is closed") }
-    }
-
-    return DefaultClientWebSocketSession(session.call, origin)
-}
-
-suspend fun HttpClient.webSocketRaw(
-    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
-    request: HttpRequestBuilder.() -> Unit = {}, block: suspend ClientWebSocketSession.() -> Unit
-): Unit {
-    val session = webSocketRawSession(method, host, port, path) {
-        url.protocol = URLProtocol.WS
-        url.port = port
-
-        request()
-    }
-
-    try {
-        session.block()
-    } catch (cause: Throwable) {
-        session.close(cause)
-    } finally {
-        session.close()
-    }
-}
-
-suspend fun HttpClient.webSocket(
-    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
-    request: HttpRequestBuilder.() -> Unit = {}, block: suspend DefaultClientWebSocketSession.() -> Unit
-): Unit {
-    val session = webSocketSession(method, host, port, path) {
-        url.protocol = URLProtocol.WS
-        url.port = port
-        request()
-    }
-
-    try {
-        session.block()
-    } catch (cause: Throwable) {
-        session.close(cause)
-    } finally {
-        session.close()
-    }
-}
-
-suspend fun HttpClient.wsRaw(
-    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
-    request: HttpRequestBuilder.() -> Unit = {}, block: suspend ClientWebSocketSession.() -> Unit
-): Unit = webSocketRaw(method, host, port, path, request, block)
-
-suspend fun HttpClient.wssRaw(
-    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
-    request: HttpRequestBuilder.() -> Unit = {}, block: suspend ClientWebSocketSession.() -> Unit
-): Unit = webSocketRaw(method, host, port, path, request = {
-    url.protocol = URLProtocol.WSS
-    url.port = port
-
-    request()
-}, block = block)
-
-suspend fun HttpClient.ws(
-    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
-    request: HttpRequestBuilder.() -> Unit = {}, block: suspend DefaultClientWebSocketSession.() -> Unit
-): Unit = webSocket(method, host, port, path, request, block)
-
-suspend fun HttpClient.wss(
-    method: HttpMethod = HttpMethod.Get, host: String = "localhost", port: Int = DEFAULT_PORT, path: String = "/",
-    request: HttpRequestBuilder.() -> Unit = {}, block: suspend DefaultClientWebSocketSession.() -> Unit
-): Unit = webSocket(method, host, port, path, request = {
-    url.protocol = URLProtocol.WSS
-    url.port = port
-
-    request()
-}, block = block)
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/test/io/ktor/client/features/websocket/WebSocketTest.kt b/ktor-client/ktor-client-features/ktor-client-websocket/jvm/test/io/ktor/client/features/websocket/WebSocketRawTest.kt
similarity index 51%
rename from ktor-client/ktor-client-features/ktor-client-websocket/jvm/test/io/ktor/client/features/websocket/WebSocketTest.kt
rename to ktor-client/ktor-client-features/ktor-client-websocket/jvm/test/io/ktor/client/features/websocket/WebSocketRawTest.kt
index 5e94d06db..ee757a508 100644
--- a/ktor-client/ktor-client-features/ktor-client-websocket/jvm/test/io/ktor/client/features/websocket/WebSocketTest.kt
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/jvm/test/io/ktor/client/features/websocket/WebSocketRawTest.kt
@@ -4,28 +4,16 @@ import io.ktor.application.*
 import io.ktor.client.engine.cio.*
 import io.ktor.client.tests.utils.*
 import io.ktor.http.cio.websocket.*
-import io.ktor.http.cio.websocket.Frame
 import io.ktor.routing.*
 import io.ktor.server.engine.*
 import io.ktor.server.netty.*
-import io.ktor.util.*
 import io.ktor.websocket.*
-import java.nio.*
 import kotlin.test.*
 
-class WebSocketTest : TestWithKtor() {
+class WebSocketRawTest : TestWithKtor() {
     override val server: ApplicationEngine = embeddedServer(Netty, serverPort) {
         install(io.ktor.websocket.WebSockets)
         routing {
-            webSocket("/ws") {
-                for (frame in incoming) {
-                    when (frame) {
-                        is Frame.Text -> send(frame)
-                        is Frame.Binary -> send(frame)
-                        else -> assert(false)
-                    }
-                }
-            }
             webSocketRaw("/rawEcho") {
                 for (frame in incoming) {
                     if (frame is Frame.Close) {
@@ -61,57 +49,6 @@ class WebSocketTest : TestWithKtor() {
         }
     }
 
-    @Test
-    fun testPingPong() = clientTest(CIO) {
-        config {
-            install(WebSockets)
-        }
-
-        test { client ->
-            client.ws(port = serverPort, path = "ws") {
-                assertTrue(masking)
-
-                repeat(10) {
-                    ping(it.toString())
-                }
-            }
-        }
-    }
-
-    @Test
-    fun testRemotePingPong(): Unit = clientTest(CIO) {
-        val remote = "echo.websocket.org"
-
-        config {
-            install(WebSockets)
-        }
-
-        test { client ->
-            client.ws(host = remote) {
-                repeat(10) {
-                    ping(it.toString())
-                }
-            }
-        }
-    }
-
-    @Test
-    fun testSecureRemotePingPong(): Unit = clientTest(CIO) {
-        val remote = "echo.websocket.org"
-
-        config {
-            install(WebSockets)
-        }
-
-        test { client ->
-            client.wss(host = remote) {
-                repeat(10) {
-                    ping(it.toString())
-                }
-            }
-        }
-    }
-
     @Test
     fun testConvenienceMethods() = clientTest(CIO) {
         config {
@@ -141,20 +78,4 @@ class WebSocketTest : TestWithKtor() {
             }
         }
     }
-
-    private suspend fun WebSocketSession.ping(salt: String) {
-        outgoing.send(Frame.Text("text: $salt"))
-        val frame = incoming.receive()
-        assert(frame is Frame.Text)
-        assertEquals("text: $salt", (frame as Frame.Text).readText())
-
-        val data = "text: $salt".toByteArray()
-        outgoing.send(Frame.Binary(true, ByteBuffer.wrap(data)))
-        val binaryFrame = incoming.receive()
-        assert(binaryFrame is Frame.Binary)
-
-        val buffer = (binaryFrame as Frame.Binary).buffer
-        val received = buffer.moveToByteArray()
-        assertEquals(data.contentToString(), received.contentToString())
-    }
 }
diff --git a/ktor-client/ktor-client-features/ktor-client-websocket/posix/src/io/ktor/client/features/websocket/WebSocketEngineNative.kt b/ktor-client/ktor-client-features/ktor-client-websocket/posix/src/io/ktor/client/features/websocket/WebSocketEngineNative.kt
new file mode 100644
index 000000000..07917b3c4
--- /dev/null
+++ b/ktor-client/ktor-client-features/ktor-client-websocket/posix/src/io/ktor/client/features/websocket/WebSocketEngineNative.kt
@@ -0,0 +1,6 @@
+package io.ktor.client.features.websocket
+
+
+internal actual fun findWebSocketEngine(): WebSocketEngine = error(
+    "Failed to find WebSocketEngine. Consider adding [WebSocketEngine] implementation in dependencies."
+)
diff --git a/ktor-client/ktor-client-ios/darwin/src/io/ktor/client/engine/ios/Ios.kt b/ktor-client/ktor-client-ios/darwin/src/io/ktor/client/engine/ios/Ios.kt
index 77029e52e..d5fbfcb41 100644
--- a/ktor-client/ktor-client-ios/darwin/src/io/ktor/client/engine/ios/Ios.kt
+++ b/ktor-client/ktor-client-ios/darwin/src/io/ktor/client/engine/ios/Ios.kt
@@ -1,12 +1,17 @@
 package io.ktor.client.engine.ios
 
 import io.ktor.client.engine.*
+import platform.Foundation.*
+import kotlin.native.concurrent.*
 
 @ThreadLocal
 private val initHook = Ios
 
+/**
+ * [HttpClientEngineFactory] using a [NSURLRequest] in implementation
+ * with the the associated configuration [HttpClientEngineConfig].
+ */
 object Ios : HttpClientEngineFactory<IosClientEngineConfig> {
-
     init {
         engines.add(this)
     }
diff --git a/ktor-client/ktor-client-okhttp/build.gradle b/ktor-client/ktor-client-okhttp/build.gradle
index 4f8522980..2f6e212f1 100644
--- a/ktor-client/ktor-client-okhttp/build.gradle
+++ b/ktor-client/ktor-client-okhttp/build.gradle
@@ -1,7 +1,9 @@
 kotlin.sourceSets {
     jvmMain.dependencies {
         api project(':ktor-client:ktor-client-core')
-        api 'com.squareup.okhttp3:okhttp:3.11.0'
+
+        api project(':ktor-client:ktor-client-features:ktor-client-websocket')
+        api "com.squareup.okhttp3:okhttp:$okhttp_version"
     }
     jvmTest.dependencies {
         api project(':ktor-client:ktor-client-tests')
diff --git a/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttp.kt b/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttp.kt
index 7295dc398..3d5ed5376 100644
--- a/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttp.kt
+++ b/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttp.kt
@@ -3,11 +3,16 @@ package io.ktor.client.engine.okhttp
 import io.ktor.client.*
 import io.ktor.client.engine.*
 
+/**
+ * [HttpClientEngineFactory] using a [OkHttp] based backend implementation
+ * with the the associated configuration [OkHttpConfig].
+ */
 object OkHttp : HttpClientEngineFactory<OkHttpConfig> {
     override fun create(block: OkHttpConfig.() -> Unit): HttpClientEngine =
         OkHttpEngine(OkHttpConfig().apply(block))
 }
 
+@Suppress("KDocMissingDocumentation")
 class OkHttpEngineContainer : HttpClientEngineContainer {
     override val factory: HttpClientEngineFactory<*> = OkHttp
 }
diff --git a/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttpEngine.kt b/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttpEngine.kt
index 7c1c79080..27433ebe6 100644
--- a/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttpEngine.kt
+++ b/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttpEngine.kt
@@ -1,8 +1,13 @@
 package io.ktor.client.engine.okhttp
+
 import io.ktor.client.call.*
 import io.ktor.client.engine.*
+import io.ktor.client.features.websocket.*
 import io.ktor.client.request.*
+import io.ktor.client.response.*
+import io.ktor.http.*
 import io.ktor.http.content.*
+import io.ktor.util.*
 import io.ktor.util.cio.*
 import io.ktor.util.date.*
 import kotlinx.coroutines.*
@@ -11,29 +16,44 @@ import kotlinx.coroutines.io.jvm.javaio.*
 import okhttp3.*
 import kotlin.coroutines.*
 
-class OkHttpEngine(override val config: OkHttpConfig) : HttpClientJvmEngine("ktor-okhttp") {
+@InternalAPI
+@Suppress("KDocMissingDocumentation")
+class OkHttpEngine(
+    override val config: OkHttpConfig
+) : HttpClientJvmEngine("ktor-okhttp"), WebSocketEngine {
+
     private val engine = OkHttpClient.Builder()
         .apply(config.config)
         .build()!!
 
     override suspend fun execute(call: HttpClientCall, data: HttpRequestData): HttpEngineCall {
         val request = DefaultHttpRequest(call, data)
-        val requestTime = GMTDate()
         val callContext = createCallContext()
+        val engineRequest = request.convertToOkHttpRequest(callContext)
+        val response = executeHttpRequest(engineRequest, callContext, call)
 
-        val builder = Request.Builder()
+        return HttpEngineCall(request, response)
+    }
 
-        with(builder) {
-            url(request.url.toString())
+    override suspend fun execute(request: HttpRequest): WebSocketResponse {
+        check(request.url.protocol.isWebsocket())
 
-            mergeHeaders(request.headers, request.content) { key, value ->
-                addHeader(key, value)
-            }
+        val callContext = createCallContext()
+        val pingInterval = engine.pingIntervalMillis().toLong()
+        val requestTime = GMTDate()
+        val engineRequest = request.convertToOkHttpRequest(callContext)
 
-            method(request.method.value, request.content.convertToOkHttpBody(callContext))
-        }
+        val session = OkHttpWebsocketSession(engine, engineRequest, callContext)
+        return WebSocketResponse(callContext, requestTime, session)
+    }
 
-        val response = engine.execute(builder.build())
+    private suspend fun executeHttpRequest(
+        engineRequest: Request,
+        callContext: CoroutineContext,
+        call: HttpClientCall
+    ): HttpResponse {
+        val requestTime = GMTDate()
+        val response = engine.execute(engineRequest)
 
         val body = response.body()
         callContext[Job]?.invokeOnCompletion { body?.close() }
@@ -45,10 +65,26 @@ class OkHttpEngine(override val config: OkHttpConfig) : HttpClientJvmEngine("kto
             ) ?: ByteReadChannel.Empty
         }
 
-        return HttpEngineCall(request, OkHttpResponse(response, call, requestTime, responseContent, callContext))
+        return OkHttpResponse(response, call, requestTime, responseContent, callContext)
     }
 }
 
+private fun HttpRequest.convertToOkHttpRequest(callContext: CoroutineContext): Request {
+    val builder = Request.Builder()
+
+    with(builder) {
+        url(url.toString())
+
+        mergeHeaders(headers, content) { key, value ->
+            addHeader(key, value)
+        }
+
+        method(method.value, content.convertToOkHttpBody(callContext))
+    }
+
+    return builder.build()!!
+}
+
 internal fun OutgoingContent.convertToOkHttpBody(callContext: CoroutineContext): RequestBody? = when (this) {
     is OutgoingContent.ByteArrayContent -> RequestBody.create(null, bytes())
     is OutgoingContent.ReadChannelContent -> StreamRequestBody(contentLength) { readFrom() }
diff --git a/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttpWebsocketSession.kt b/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttpWebsocketSession.kt
new file mode 100644
index 000000000..0fc4f9ce4
--- /dev/null
+++ b/ktor-client/ktor-client-okhttp/jvm/src/io/ktor/client/engine/okhttp/OkHttpWebsocketSession.kt
@@ -0,0 +1,102 @@
+package io.ktor.client.engine.okhttp
+
+import io.ktor.client.features.websocket.*
+import io.ktor.http.cio.websocket.*
+import io.ktor.util.*
+import kotlinx.coroutines.*
+import kotlinx.coroutines.channels.*
+import okhttp3.*
+import okio.*
+import kotlin.coroutines.*
+
+internal class OkHttpWebsocketSession(
+    private val engine: OkHttpClient,
+    engineRequest: Request,
+    override val coroutineContext: CoroutineContext
+) : DefaultWebSocketSession, WebSocketListener() {
+    private val websocket: WebSocket = engine.newWebSocket(engineRequest, this)
+
+    override var pingIntervalMillis: Long
+        get() = engine.pingIntervalMillis().toLong()
+        set(_) = throw WebSocketException("OkHttp doesn't support dynamic ping interval. You could switch it in the engine configuration.")
+
+    override var timeoutMillis: Long
+        get() = engine.readTimeoutMillis().toLong()
+        set(_) = throw WebSocketException("Websocket timeout should be configured in OkHttpEngine.")
+
+    override var masking: Boolean
+        get() = true
+        set(_) = throw WebSocketException("Masking switch is not supported in OkHttp engine.")
+
+    override var maxFrameSize: Long
+        get() = throw WebSocketException("OkHttp websocket doesn't support max frame size.")
+        set(_) = throw WebSocketException("Websocket timeout should be configured in OkHttpEngine.")
+
+    private val _incoming = Channel<Frame>()
+    private val _closeReason = CompletableDeferred<CloseReason?>()
+
+    override val incoming: ReceiveChannel<Frame>
+        get() = _incoming
+
+    override val closeReason: Deferred<CloseReason?>
+        get() = _closeReason
+
+    override val outgoing: SendChannel<Frame> = actor {
+        try {
+            for (frame in channel) {
+                when (frame) {
+                    is Frame.Binary -> websocket.send(ByteString.of(frame.data, 0, frame.data.size))
+                    is Frame.Text -> websocket.send(String(frame.data))
+                    is Frame.Close -> {
+                        val reason = frame.readReason()!!
+                        websocket.close(reason.code.toInt(), reason.message)
+                        return@actor
+                    }
+                    else -> throw UnsupportedFrameTypeException(frame)
+                }
+            }
+        } finally {
+            websocket.close(CloseReason.Codes.UNEXPECTED_CONDITION.code.toInt(), "Client failure")
+        }
+    }
+
+    override fun onMessage(webSocket: WebSocket, bytes: ByteString) {
+        super.onMessage(webSocket, bytes)
+        _incoming.sendBlocking(Frame.Binary(true, bytes.toByteArray()))
+    }
+
+    override fun onMessage(webSocket: WebSocket, text: String) {
+        super.onMessage(webSocket, text)
+        _incoming.sendBlocking(Frame.Text(true, text.toByteArray()))
+    }
+
+    override fun onClosed(webSocket: WebSocket, code: Int, reason: String) {
+        super.onClosed(webSocket, code, reason)
+
+        _closeReason.complete(CloseReason(code.toShort(), reason))
+        _incoming.close()
+        outgoing.close()
+    }
+
+    override fun onFailure(webSocket: WebSocket, t: Throwable, response: Response?) {
+        super.onFailure(webSocket, t, response)
+
+        _incoming.close(t)
+        outgoing.close(t)
+    }
+
+    override suspend fun flush() {
+    }
+
+    override fun terminate() {
+        coroutineContext.cancel()
+    }
+
+    @KtorExperimentalAPI
+    override suspend fun close(cause: Throwable?) {
+        outgoing.close(cause)
+    }
+}
+
+@Suppress("KDocMissingDocumentation")
+class UnsupportedFrameTypeException(frame: Frame) : IllegalArgumentException("Unsupported frame type: $frame")
diff --git a/ktor-client/ktor-client-tests/build.gradle b/ktor-client/ktor-client-tests/build.gradle
index f08f7e829..4356ced21 100644
--- a/ktor-client/ktor-client-tests/build.gradle
+++ b/ktor-client/ktor-client-tests/build.gradle
@@ -3,8 +3,11 @@ description = 'Common tests for client'
 apply plugin: "kotlinx-serialization"
 
 kotlin.sourceSets {
-    jvmMain.dependencies {
+    commonMain.dependencies {
         api project(':ktor-client:ktor-client-core')
+        api project(':ktor-client:ktor-client-tests:ktor-client-tests-dispatcher')
+    }
+    jvmMain.dependencies {
         api project(':ktor-server:ktor-server-jetty')
         api project(':ktor-server:ktor-server-netty')
         api group: 'ch.qos.logback', name: 'logback-classic', version: logback_version
@@ -15,5 +18,17 @@ kotlin.sourceSets {
         runtimeOnly project(':ktor-client:ktor-client-apache')
         runtimeOnly project(':ktor-client:ktor-client-cio')
     }
-}
+    if (!project.ext.ideaActive) {
+        configure([linuxX64Test, mingwX64Test, macosX64Test]) {
+            dependencies {
+                api project(':ktor-client:ktor-client-curl')
+            }
+        }
 
+        configure([iosX64Test, iosArm32Test, iosArm64Test, macosX64Test]) {
+            dependencies {
+                api project(':ktor-client:ktor-client-ios')
+            }
+        }
+    }
+}
diff --git a/ktor-client/ktor-client-tests/common/src/io/ktor/client/tests/utils/CommonClientTestUtils.kt b/ktor-client/ktor-client-tests/common/src/io/ktor/client/tests/utils/CommonClientTestUtils.kt
new file mode 100644
index 000000000..2ad750fa1
--- /dev/null
+++ b/ktor-client/ktor-client-tests/common/src/io/ktor/client/tests/utils/CommonClientTestUtils.kt
@@ -0,0 +1,74 @@
+package io.ktor.client.tests.utils
+
+import io.ktor.client.*
+import io.ktor.client.engine.*
+import io.ktor.client.tests.utils.dispatcher.*
+import io.ktor.util.*
+import kotlinx.coroutines.*
+import kotlinx.io.core.*
+
+/**
+ * Perform test against all clients from dependencies.
+ */
+expect fun clientsTest(
+    block: suspend TestClientBuilder<HttpClientEngineConfig>.() -> Unit
+)
+
+/**
+ * Perform test with selected client [engine].
+ */
+fun clientTest(
+    engine: HttpClientEngine,
+    block: suspend TestClientBuilder<*>.() -> Unit
+) = clientTest(HttpClient(engine), block)
+
+/**
+ * Perform test with selected [client] or client loaded by service loader.
+ */
+fun clientTest(
+    client: HttpClient = HttpClient(),
+    block: suspend TestClientBuilder<HttpClientEngineConfig>.() -> Unit
+) = testSuspend {
+    val builder = TestClientBuilder<HttpClientEngineConfig>().also { it.block() }
+
+    @Suppress("UNCHECKED_CAST")
+    client
+        .config { builder.config(this as HttpClientConfig<HttpClientEngineConfig>) }
+        .use { client -> builder.test(client) }
+}
+
+/**
+ * Perform test with selected client engine [factory].
+ */
+fun <T : HttpClientEngineConfig> clientTest(
+    factory: HttpClientEngineFactory<T>,
+    block: suspend TestClientBuilder<T>.() -> Unit
+) = testSuspend {
+    val builder = TestClientBuilder<T>().apply { block() }
+    val client = HttpClient(factory, block = builder.config)
+
+    client.use {
+        builder.test(it)
+    }
+
+    client.coroutineContext[Job]!!.join()
+}
+
+@InternalAPI
+@Suppress("KDocMissingDocumentation")
+class TestClientBuilder<T : HttpClientEngineConfig>(
+    var config: HttpClientConfig<T>.() -> Unit = {},
+    var test: suspend (client: HttpClient) -> Unit = {}
+)
+
+@InternalAPI
+@Suppress("KDocMissingDocumentation")
+fun <T : HttpClientEngineConfig> TestClientBuilder<T>.config(block: HttpClientConfig<T>.() -> Unit): Unit {
+    config = block
+}
+
+@InternalAPI
+@Suppress("KDocMissingDocumentation")
+fun TestClientBuilder<*>.test(block: suspend (client: HttpClient) -> Unit): Unit {
+    test = block
+}
diff --git a/ktor-client/ktor-client-tests/jvm/test/io/ktor/client/tests/DefaultEngineTest.kt b/ktor-client/ktor-client-tests/common/test/io/ktor/client/tests/DefaultEngineTest.kt
similarity index 99%
rename from ktor-client/ktor-client-tests/jvm/test/io/ktor/client/tests/DefaultEngineTest.kt
rename to ktor-client/ktor-client-tests/common/test/io/ktor/client/tests/DefaultEngineTest.kt
index e6ae5d1f9..00bca9de6 100644
--- a/ktor-client/ktor-client-tests/jvm/test/io/ktor/client/tests/DefaultEngineTest.kt
+++ b/ktor-client/ktor-client-tests/common/test/io/ktor/client/tests/DefaultEngineTest.kt
@@ -4,7 +4,6 @@ import io.ktor.client.*
 import kotlin.test.*
 
 class DefaultEngineTest {
-
     @Test
     fun instantiationTest() {
         val client = HttpClient()
diff --git a/ktor-client/ktor-client-tests/js/src/io/ktor/client/tests/utils/JsClientTestUtils.kt b/ktor-client/ktor-client-tests/js/src/io/ktor/client/tests/utils/JsClientTestUtils.kt
new file mode 100644
index 000000000..918930b65
--- /dev/null
+++ b/ktor-client/ktor-client-tests/js/src/io/ktor/client/tests/utils/JsClientTestUtils.kt
@@ -0,0 +1,10 @@
+package io.ktor.client.tests.utils
+
+import io.ktor.client.engine.*
+
+/**
+ * Perform test against all clients from dependencies.
+ */
+actual fun clientsTest(
+    block: suspend TestClientBuilder<HttpClientEngineConfig>.() -> Unit
+) = clientTest(block = block)
diff --git a/ktor-client/ktor-client-tests/jvm/src/io/ktor/client/tests/utils/ClientTestUtils.kt b/ktor-client/ktor-client-tests/jvm/src/io/ktor/client/tests/utils/ClientTestUtils.kt
index 070e7c471..32ebfa4b8 100644
--- a/ktor-client/ktor-client-tests/jvm/src/io/ktor/client/tests/utils/ClientTestUtils.kt
+++ b/ktor-client/ktor-client-tests/jvm/src/io/ktor/client/tests/utils/ClientTestUtils.kt
@@ -2,48 +2,19 @@ package io.ktor.client.tests.utils
 
 import io.ktor.client.*
 import io.ktor.client.engine.*
-import kotlinx.coroutines.*
+import java.util.*
 
-fun <T : HttpClientEngineConfig> clientTest(
-    factory: HttpClientEngineFactory<T>,
-    block: suspend TestClientBuilder<T>.() -> Unit
-): Unit = runBlocking {
-    val builder = TestClientBuilder<T>().apply { block() }
-    val client = HttpClient(factory, block = builder.config)
-
-    client.use {
-        builder.test(it)
+/**
+ * Perform test against all clients from dependencies.
+ */
+actual fun clientsTest(
+    block: suspend TestClientBuilder<HttpClientEngineConfig>.() -> Unit
+): Unit {
+    val engines: List<HttpClientEngineContainer> = HttpClientEngineContainer::class.java.let {
+        ServiceLoader.load(it, it.classLoader).toList()
     }
 
-    client.coroutineContext[Job]!!.join()
-}
-
-fun clientTest(
-    engine: HttpClientEngine,
-    block: suspend TestClientBuilder<*>.() -> Unit
-): Unit = clientTest(HttpClient(engine), block)
-
-fun clientTest(
-    client: HttpClient = HttpClient(),
-    block: suspend TestClientBuilder<HttpClientEngineConfig>.() -> Unit
-): Unit = runBlocking {
-    val builder = TestClientBuilder<HttpClientEngineConfig>().also { it.block() }
-
-    @Suppress("UNCHECKED_CAST")
-    client
-        .config { builder.config(this as HttpClientConfig<HttpClientEngineConfig>) }
-        .use { client -> builder.test(client) }
-}
-
-class TestClientBuilder<T : HttpClientEngineConfig>(
-    var config: HttpClientConfig<T>.() -> Unit = {},
-    var test: suspend (client: HttpClient) -> Unit = {}
-)
-
-fun <T : HttpClientEngineConfig> TestClientBuilder<T>.config(block: HttpClientConfig<T>.() -> Unit): Unit {
-    config = block
-}
-
-fun TestClientBuilder<*>.test(block: suspend (client: HttpClient) -> Unit): Unit {
-    test = block
+    engines.forEach {
+        clientTest(it.factory, block)
+    }
 }
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/common/src/TestCommon.kt b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/common/src/TestCommon.kt
new file mode 100644
index 000000000..4fc44322b
--- /dev/null
+++ b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/common/src/TestCommon.kt
@@ -0,0 +1,13 @@
+package io.ktor.client.tests.utils.dispatcher
+
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
+
+/**
+ * Test runner for common suspend tests.
+ */
+@Suppress("NO_ACTUAL_FOR_EXPECT")
+expect fun testSuspend(
+    context: CoroutineContext = EmptyCoroutineContext,
+    block: suspend CoroutineScope.() -> Unit
+)
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/iosArm32/src/TestIosArm32.kt b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/iosArm32/src/TestIosArm32.kt
new file mode 100644
index 000000000..fbcdc0368
--- /dev/null
+++ b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/iosArm32/src/TestIosArm32.kt
@@ -0,0 +1,25 @@
+@file:Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
+
+package io.ktor.client.tests.utils.dispatcher
+
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
+import platform.Foundation.*
+
+/**
+ * Test runner for native suspend tests.
+ */
+actual fun testSuspend(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> Unit
+): Unit = runBlocking {
+    val loop = coroutineContext[ContinuationInterceptor] as EventLoop
+
+    val task = launch { block() }
+    while (!task.isCompleted) {
+        val date = NSDate().addTimeInterval(1.0) as NSDate
+        NSRunLoop.mainRunLoop.runUntilDate(date)
+
+        loop.processNextEvent()
+    }
+}
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/iosArm64/src/TestIosArm64.kt b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/iosArm64/src/TestIosArm64.kt
new file mode 100644
index 000000000..fbcdc0368
--- /dev/null
+++ b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/iosArm64/src/TestIosArm64.kt
@@ -0,0 +1,25 @@
+@file:Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
+
+package io.ktor.client.tests.utils.dispatcher
+
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
+import platform.Foundation.*
+
+/**
+ * Test runner for native suspend tests.
+ */
+actual fun testSuspend(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> Unit
+): Unit = runBlocking {
+    val loop = coroutineContext[ContinuationInterceptor] as EventLoop
+
+    val task = launch { block() }
+    while (!task.isCompleted) {
+        val date = NSDate().addTimeInterval(1.0) as NSDate
+        NSRunLoop.mainRunLoop.runUntilDate(date)
+
+        loop.processNextEvent()
+    }
+}
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/iosX64/src/TestIosX64.kt b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/iosX64/src/TestIosX64.kt
new file mode 100644
index 000000000..fbcdc0368
--- /dev/null
+++ b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/iosX64/src/TestIosX64.kt
@@ -0,0 +1,25 @@
+@file:Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
+
+package io.ktor.client.tests.utils.dispatcher
+
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
+import platform.Foundation.*
+
+/**
+ * Test runner for native suspend tests.
+ */
+actual fun testSuspend(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> Unit
+): Unit = runBlocking {
+    val loop = coroutineContext[ContinuationInterceptor] as EventLoop
+
+    val task = launch { block() }
+    while (!task.isCompleted) {
+        val date = NSDate().addTimeInterval(1.0) as NSDate
+        NSRunLoop.mainRunLoop.runUntilDate(date)
+
+        loop.processNextEvent()
+    }
+}
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/js/src/TestJs.kt b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/js/src/TestJs.kt
new file mode 100644
index 000000000..edc09b0fb
--- /dev/null
+++ b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/js/src/TestJs.kt
@@ -0,0 +1,12 @@
+package io.ktor.client.tests.utils.dispatcher
+
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
+
+/**
+ * Test runner for js suspend tests.
+ */
+actual fun testSuspend(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> Unit
+): dynamic = GlobalScope.promise(block = block, context = context)
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/jvm/src/TestJvm.kt b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/jvm/src/TestJvm.kt
new file mode 100644
index 000000000..86cf98a9e
--- /dev/null
+++ b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/jvm/src/TestJvm.kt
@@ -0,0 +1,12 @@
+package io.ktor.client.tests.utils.dispatcher
+
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
+
+/**
+ * Test runner for jvm suspend tests.
+ */
+actual fun testSuspend(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> Unit
+): Unit = runBlocking(context, block)
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/linuxX64/src/TestLinuxX64.kt b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/linuxX64/src/TestLinuxX64.kt
new file mode 100644
index 000000000..535c8d9a8
--- /dev/null
+++ b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/linuxX64/src/TestLinuxX64.kt
@@ -0,0 +1,12 @@
+package io.ktor.client.tests.utils.dispatcher
+
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
+
+/**
+ * Test runner for native suspend tests.
+ */
+actual fun testSuspend(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> Unit
+): Unit = runBlocking(context, block)
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/macosX64/src/TestMacosX64.kt b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/macosX64/src/TestMacosX64.kt
new file mode 100644
index 000000000..fbcdc0368
--- /dev/null
+++ b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/macosX64/src/TestMacosX64.kt
@@ -0,0 +1,25 @@
+@file:Suppress("INVISIBLE_MEMBER", "INVISIBLE_REFERENCE")
+
+package io.ktor.client.tests.utils.dispatcher
+
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
+import platform.Foundation.*
+
+/**
+ * Test runner for native suspend tests.
+ */
+actual fun testSuspend(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> Unit
+): Unit = runBlocking {
+    val loop = coroutineContext[ContinuationInterceptor] as EventLoop
+
+    val task = launch { block() }
+    while (!task.isCompleted) {
+        val date = NSDate().addTimeInterval(1.0) as NSDate
+        NSRunLoop.mainRunLoop.runUntilDate(date)
+
+        loop.processNextEvent()
+    }
+}
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/mingwX64/src/TestMingwX64.kt b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/mingwX64/src/TestMingwX64.kt
new file mode 100644
index 000000000..535c8d9a8
--- /dev/null
+++ b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/mingwX64/src/TestMingwX64.kt
@@ -0,0 +1,12 @@
+package io.ktor.client.tests.utils.dispatcher
+
+import kotlinx.coroutines.*
+import kotlin.coroutines.*
+
+/**
+ * Test runner for native suspend tests.
+ */
+actual fun testSuspend(
+    context: CoroutineContext,
+    block: suspend CoroutineScope.() -> Unit
+): Unit = runBlocking(context, block)
diff --git a/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/posix/src/.gitkeep b/ktor-client/ktor-client-tests/ktor-client-tests-dispatcher/posix/src/.gitkeep
new file mode 100644
index 000000000..e69de29bb
diff --git a/ktor-client/ktor-client-tests/posix/src/io/ktor/client/tests/utils/NativeClientTestUtils.kt b/ktor-client/ktor-client-tests/posix/src/io/ktor/client/tests/utils/NativeClientTestUtils.kt
new file mode 100644
index 000000000..8c4346ad3
--- /dev/null
+++ b/ktor-client/ktor-client-tests/posix/src/io/ktor/client/tests/utils/NativeClientTestUtils.kt
@@ -0,0 +1,12 @@
+package io.ktor.client.tests.utils
+
+import io.ktor.client.engine.*
+
+/**
+ * Perform test against all clients from dependencies.
+ */
+actual fun clientsTest(
+    block: suspend TestClientBuilder<HttpClientEngineConfig>.() -> Unit
+) {
+    engines.forEach { clientTest(it, block) }
+}
diff --git a/ktor-features/build.gradle b/ktor-features/build.gradle
index 65d236276..cebe197fa 100644
--- a/ktor-features/build.gradle
+++ b/ktor-features/build.gradle
@@ -1,16 +1,11 @@
+
 subprojects {
-    kotlin {
-        sourceSets {
-            commonMain {
-                dependencies {
-                    api project(':ktor-server:ktor-server-core')
-                }
-            }
-            commonTest {
-                dependencies {
-                    api project(":ktor-server:ktor-server-test-host")
-                }
-            }
+    kotlin.sourceSets {
+        commonMain.dependencies {
+            api project(':ktor-server:ktor-server-core')
+        }
+        commonTest.dependencies {
+            api project(":ktor-server:ktor-server-test-host")
         }
     }
 }
diff --git a/ktor-features/ktor-websockets/jvm/src/io/ktor/websocket/Routing.kt b/ktor-features/ktor-websockets/jvm/src/io/ktor/websocket/Routing.kt
index bfe3a18d0..e05c8bdd8 100644
--- a/ktor-features/ktor-websockets/jvm/src/io/ktor/websocket/Routing.kt
+++ b/ktor-features/ktor-websockets/jvm/src/io/ktor/websocket/Routing.kt
@@ -138,7 +138,7 @@ private class WebSocketProtocolsSelector(
 ) : RouteSelector(RouteSelectorEvaluation.qualityConstant) {
     override fun evaluate(context: RoutingResolveContext, segmentIndex: Int): RouteSelectorEvaluation {
         val protocols = context.call.request.headers[HttpHeaders.SecWebSocketProtocol]
-                ?: return RouteSelectorEvaluation.Failed
+            ?: return RouteSelectorEvaluation.Failed
 
         if (requiredProtocol in parseHeaderValue(protocols).map { it.value }) {
             return RouteSelectorEvaluation.Constant
diff --git a/ktor-features/ktor-websockets/jvm/test/io/ktor/tests/websocket/WebSocketEngineSuite.kt b/ktor-features/ktor-websockets/jvm/test/io/ktor/tests/websocket/WebSocketEngineSuite.kt
index eacff9d50..411387c9b 100644
--- a/ktor-features/ktor-websockets/jvm/test/io/ktor/tests/websocket/WebSocketEngineSuite.kt
+++ b/ktor-features/ktor-websockets/jvm/test/io/ktor/tests/websocket/WebSocketEngineSuite.kt
@@ -26,7 +26,9 @@ import java.util.concurrent.CancellationException
 import kotlin.test.*
 
 @UseExperimental(WebSocketInternalAPI::class, ObsoleteCoroutinesApi::class)
-abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration : ApplicationEngine.Configuration>(hostFactory: ApplicationEngineFactory<TEngine, TConfiguration>) : EngineTestBase<TEngine, TConfiguration>(hostFactory) {
+abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration : ApplicationEngine.Configuration>(
+    hostFactory: ApplicationEngineFactory<TEngine, TConfiguration>
+) : EngineTestBase<TEngine, TConfiguration>(hostFactory) {
     @get:Rule
     val errors = ErrorCollector()
 
@@ -57,7 +59,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
         socket {
             // send upgrade request
             outputStream.apply {
-                write("""
+                write(
+                    """
                 GET / HTTP/1.1
                 Host: localhost:$port
                 Upgrade: websocket
@@ -66,7 +69,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
                 Origin: http://localhost:$port
                 Sec-WebSocket-Protocol: chat
                 Sec-WebSocket-Version: 13
-                """.trimIndent().replace("\n", "\r\n").toByteArray())
+                """.trimIndent().replace("\n", "\r\n").toByteArray()
+                )
                 write("\r\n\r\n".toByteArray())
                 flush()
             }
@@ -114,7 +118,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
         socket {
             // send upgrade request
             outputStream.apply {
-                write("""
+                write(
+                    """
                 GET / HTTP/1.1
                 Host: localhost:$port
                 Upgrade: websocket
@@ -123,7 +128,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
                 Origin: http://localhost:$port
                 Sec-WebSocket-Protocol: chat
                 Sec-WebSocket-Version: 13
-                """.trimIndent().replace("\n", "\r\n").toByteArray())
+                """.trimIndent().replace("\n", "\r\n").toByteArray()
+                )
                 write("\r\n\r\n".toByteArray())
                 flush()
             }
@@ -189,7 +195,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
         socket {
             // send upgrade request
             outputStream.apply {
-                write("""
+                write(
+                    """
                 GET / HTTP/1.1
                 Host: localhost:$port
                 Upgrade: websocket
@@ -198,7 +205,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
                 Origin: http://localhost:$port
                 Sec-WebSocket-Protocol: chat
                 Sec-WebSocket-Version: 13
-                """.trimIndent().replace("\n", "\r\n").toByteArray())
+                """.trimIndent().replace("\n", "\r\n").toByteArray()
+                )
                 write("\r\n\r\n".toByteArray())
                 flush()
             }
@@ -250,7 +258,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
         socket {
             // send upgrade request
             outputStream.apply {
-                write("""
+                write(
+                    """
                 GET / HTTP/1.1
                 Host: localhost:$port
                 Upgrade: websocket
@@ -259,7 +268,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
                 Origin: http://localhost:$port
                 Sec-WebSocket-Protocol: chat
                 Sec-WebSocket-Version: 13
-                """.trimIndent().replace("\n", "\r\n").toByteArray())
+                """.trimIndent().replace("\n", "\r\n").toByteArray()
+                )
                 write("\r\n\r\n".toByteArray())
                 flush()
             }
@@ -317,7 +327,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
         socket {
             // send upgrade request
             outputStream.apply {
-                write("""
+                write(
+                    """
                 GET / HTTP/1.1
                 Host: localhost:$port
                 Upgrade: websocket
@@ -326,7 +337,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
                 Origin: http://localhost:$port
                 Sec-WebSocket-Protocol: chat
                 Sec-WebSocket-Version: 13
-                """.trimIndent().replace("\n", "\r\n").toByteArray())
+                """.trimIndent().replace("\n", "\r\n").toByteArray()
+                )
                 write("\r\n\r\n".toByteArray())
                 flush()
             }
@@ -399,7 +411,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
         socket {
             // send upgrade request
             outputStream.apply {
-                write("""
+                write(
+                    """
                 GET / HTTP/1.1
                 Host: localhost:$port
                 Upgrade: websocket
@@ -408,7 +421,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
                 Origin: http://localhost:$port
                 Sec-WebSocket-Protocol: chat
                 Sec-WebSocket-Version: 13
-                """.trimIndent().replace("\n", "\r\n").toByteArray())
+                """.trimIndent().replace("\n", "\r\n").toByteArray()
+                )
                 write("\r\n\r\n".toByteArray())
                 flush()
             }
@@ -462,7 +476,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
         socket {
             // send upgrade request
             outputStream.apply {
-                write("""
+                write(
+                    """
                 GET / HTTP/1.1
                 Host: localhost:$port
                 Upgrade: websocket
@@ -471,7 +486,8 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
                 Origin: http://localhost:$port
                 Sec-WebSocket-Protocol: chat
                 Sec-WebSocket-Version: 13
-                """.trimIndent().replace("\n", "\r\n").toByteArray())
+                """.trimIndent().replace("\n", "\r\n").toByteArray()
+                )
                 write("\r\n\r\n".toByteArray())
                 flush()
             }
@@ -503,8 +519,10 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
         }
     }
 
-    private fun Socket.assertCloseFrame(closeCode: Short = CloseReason.Codes.NORMAL.code,
-                                        replyCloseFrame: Boolean = true) {
+    private fun Socket.assertCloseFrame(
+        closeCode: Short = CloseReason.Codes.NORMAL.code,
+        replyCloseFrame: Boolean = true
+    ) {
         loop@
         while (true) {
             val frame = getInputStream().readFrame()
@@ -529,9 +547,10 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
         val opcodeAndFin = readOrFail()
         val lenAndMask = readOrFail()
 
-        val frameType = FrameType[opcodeAndFin and 0x0f] ?: throw IllegalStateException("Wrong opcode ${opcodeAndFin and 0x0f}")
-        val fin = (opcodeAndFin and 0x80) != 0
+        val frameType = FrameType[opcodeAndFin and 0x0f]
+            ?: throw IllegalStateException("Wrong opcode ${opcodeAndFin and 0x0f}")
 
+        val fin = (opcodeAndFin and 0x80) != 0
         val len1 = lenAndMask and 0x7f
         val mask = (lenAndMask and 0x80) != 0
 
@@ -600,13 +619,13 @@ abstract class WebSocketEngineSuite<TEngine : ApplicationEngine, TConfiguration
 
     private fun InputStream.readShortBE() = (readOrFail() shl 8) or readOrFail()
     private fun InputStream.readLongBE() = (readOrFail().toLong() shl 56) or
-            (readOrFail().toLong() shl 48) or
-            (readOrFail().toLong() shl 40) or
-            (readOrFail().toLong() shl 32) or
-            (readOrFail().toLong() shl 24) or
-            (readOrFail().toLong() shl 16) or
-            (readOrFail().toLong() shl 8) or
-            readOrFail().toLong()
+        (readOrFail().toLong() shl 48) or
+        (readOrFail().toLong() shl 40) or
+        (readOrFail().toLong() shl 32) or
+        (readOrFail().toLong() shl 24) or
+        (readOrFail().toLong() shl 16) or
+        (readOrFail().toLong() shl 8) or
+        readOrFail().toLong()
 
     private fun InputStream.readFully(size: Int): ByteArray {
         val array = ByteArray(size)
diff --git a/ktor-utils/common/src/io/ktor/util/Base64.kt b/ktor-utils/common/src/io/ktor/util/Base64.kt
index 70430c208..298627d73 100644
--- a/ktor-utils/common/src/io/ktor/util/Base64.kt
+++ b/ktor-utils/common/src/io/ktor/util/Base64.kt
@@ -19,6 +19,14 @@ fun String.encodeBase64(): String = buildPacket {
     writeStringUtf8(this@encodeBase64)
 }.encodeBase64()
 
+/**
+ * Encode [ByteArray] in base64 format
+ */
+@InternalAPI
+fun ByteArray.encodeBase64(): String = buildPacket {
+    writeFully(this@encodeBase64)
+}.encodeBase64()
+
 /**
  * Encode [ByteReadPacket] in base64 format
  */
diff --git a/ktor-utils/common/src/io/ktor/util/Bytes.kt b/ktor-utils/common/src/io/ktor/util/Bytes.kt
new file mode 100644
index 000000000..58715513c
--- /dev/null
+++ b/ktor-utils/common/src/io/ktor/util/Bytes.kt
@@ -0,0 +1,10 @@
+package io.ktor.util
+
+/**
+ * Read [Short] with specified [offset] from [ByteArray].
+ */
+@InternalAPI
+fun ByteArray.readShort(offset: Int): Short {
+    val result = ((this[offset].toInt() and 0xFF) shl 8) or (this[offset + 1].toInt() and 0xFF)
+    return result.toShort()
+}
diff --git a/ktor-utils/common/src/io/ktor/util/Crypto.kt b/ktor-utils/common/src/io/ktor/util/Crypto.kt
index 33245011d..d9601e8c3 100644
--- a/ktor-utils/common/src/io/ktor/util/Crypto.kt
+++ b/ktor-utils/common/src/io/ktor/util/Crypto.kt
@@ -1,5 +1,6 @@
 @file:kotlin.jvm.JvmMultifileClass
 @file:kotlin.jvm.JvmName("CryptoKt")
+
 package io.ktor.util
 
 import kotlinx.io.charsets.*
@@ -51,6 +52,12 @@ fun generateNonce(size: Int): ByteArray = buildPacket {
     }
 }.readBytes(size)
 
+/**
+ * Compute SHA-1 hash for the specified [bytes]
+ */
+@KtorExperimentalAPI
+expect fun sha1(bytes: ByteArray): ByteArray
+
 @InternalAPI
 expect fun Digest(name: String): Digest
 
diff --git a/ktor-utils/js/src/io/ktor/util/CryptoJs.kt b/ktor-utils/js/src/io/ktor/util/CryptoJs.kt
index ce02e58be..69c80da90 100644
--- a/ktor-utils/js/src/io/ktor/util/CryptoJs.kt
+++ b/ktor-utils/js/src/io/ktor/util/CryptoJs.kt
@@ -40,3 +40,11 @@ private external object crypto {
 private external class SubtleCrypto {
     fun digest(algoName: String, buffer: ByteArray): Promise<ArrayBuffer>
 }
+
+/**
+ * Compute SHA-1 hash for the specified [bytes]
+ */
+@KtorExperimentalAPI
+actual fun sha1(bytes: ByteArray): ByteArray {
+    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
+}
diff --git a/ktor-utils/jvm/src/io/ktor/util/CryptoJvm.kt b/ktor-utils/jvm/src/io/ktor/util/CryptoJvm.kt
index 08f086c93..2633b6a78 100644
--- a/ktor-utils/jvm/src/io/ktor/util/CryptoJvm.kt
+++ b/ktor-utils/jvm/src/io/ktor/util/CryptoJvm.kt
@@ -1,5 +1,6 @@
 @file:kotlin.jvm.JvmMultifileClass
 @file:kotlin.jvm.JvmName("CryptoKt")
+
 package io.ktor.util
 
 import kotlinx.coroutines.*
@@ -22,7 +23,11 @@ private fun getDigest(text: String, algorithm: String, salt: String): ByteArray
  * Compute SHA-1 hash for the specified [bytes]
  */
 @KtorExperimentalAPI
-fun sha1(bytes: ByteArray): ByteArray = MessageDigest.getInstance("SHA1").digest(bytes)!!
+actual fun sha1(bytes: ByteArray): ByteArray = runBlocking {
+    Digest("SHA1").also { it += bytes }.build()
+}
+
+actual fun Digest(name: String): Digest = DigestImpl(MessageDigest.getInstance(name))
 
 private inline class DigestImpl(val delegate: MessageDigest) : Digest {
     override fun plusAssign(bytes: ByteArray) {
diff --git a/ktor-utils/posix/interop/utils.def b/ktor-utils/posix/interop/utils.def
index 8e6de9b0f..5b480d0ff 100644
--- a/ktor-utils/posix/interop/utils.def
+++ b/ktor-utils/posix/interop/utils.def
@@ -1,5 +1,10 @@
 package = utils
 compilerOpts.mingw_x64 = -DMINGW
+compilerOpts.ios_x64 = -DIOS
+compilerOpts.ios_arm64 = -DIOS
+compilerOpts.ios_arm32 = -DIOS
+compilerOpts.macos_x64 = -DMACOS
+compilerOpts.linux_x64 = -DLINUX
 ---
 #include <pthread.h>
 #include <time.h>
diff --git a/ktor-utils/posix/src/io/ktor/util/CryptoNative.kt b/ktor-utils/posix/src/io/ktor/util/CryptoNative.kt
index 62056a2ca..3b52e8b14 100644
--- a/ktor-utils/posix/src/io/ktor/util/CryptoNative.kt
+++ b/ktor-utils/posix/src/io/ktor/util/CryptoNative.kt
@@ -5,3 +5,11 @@ actual fun generateNonce(): String = error("[generateNonce] is not supported on
 
 @InternalAPI
 actual fun Digest(name: String): Digest = error("[Digest] is not supported on iOS")
+
+/**
+ * Compute SHA-1 hash for the specified [bytes]
+ */
+@KtorExperimentalAPI
+actual fun sha1(bytes: ByteArray): ByteArray {
+    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
+}
diff --git a/settings.gradle b/settings.gradle
index 60c70262d..33e1a605c 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -31,6 +31,7 @@ includeEx ':ktor-server'
 includeEx ':ktor-client'
 includeEx ':ktor-client:ktor-client-core'
 includeEx ':ktor-client:ktor-client-tests'
+includeEx ':ktor-client:ktor-client-tests:ktor-client-tests-dispatcher'
 includeEx ':ktor-client:ktor-client-apache'
 includeEx ':ktor-client:ktor-client-android'
 includeEx ':ktor-client:ktor-client-cio'