diff --git a/build.gradle.kts b/build.gradle.kts
index 8de9756..aa75348 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -1,5 +1,6 @@
 val ktor_version: String by project
 val kotlin_version: String by project
+val logback_version: String by project
 
 plugins {
     kotlin("multiplatform") version "1.7.10"
@@ -58,9 +59,18 @@ kotlin {
         val jvmMain by getting {
             dependencies {
                 implementation("org.mapdb:mapdb:3.0.8")
+                implementation("io.ktor:ktor-client-cio-jvm:$ktor_version")
+                implementation("io.ktor:ktor-server-websockets:$ktor_version")
+            }
+        }
+        val jvmTest by getting {
+            dependencies {
+                implementation("io.ktor:ktor-server-core:$ktor_version")
+                implementation("io.ktor:ktor-server-netty:$ktor_version")
+                implementation("ch.qos.logback:logback-classic:$logback_version")
+
             }
         }
-        val jvmTest by getting
         val jsMain by getting
         val jsTest by getting
     }
diff --git a/gradle.properties b/gradle.properties
index 56a75d8..743d342 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -2,4 +2,5 @@ kotlin.code.style=official
 kotlin.mpp.enableGranularSourceSetsMetadata=true
 kotlin.native.enableDependencyPropagation=false
 kotlin.js.generate.executable.default=false
-ktor_version=2.1.0
+ktor_version=2.1.1
+logback_version=1.2.10
diff --git a/src/commonMain/kotlin/net.sergeych.parsec3/Adapter.kt b/src/commonMain/kotlin/net.sergeych.parsec3/Adapter.kt
index e923415..5ffcb82 100644
--- a/src/commonMain/kotlin/net.sergeych.parsec3/Adapter.kt
+++ b/src/commonMain/kotlin/net.sergeych.parsec3/Adapter.kt
@@ -117,8 +117,12 @@ open class Adapter<T>(
                 } catch (ae: ParsecException) {
                     sendPackage(Package.Response(pe.id, null, ae.code, ae.text))
                 } catch (ex: Throwable) {
-                    ex.printStackTrace()
-                    sendPackage(Package.Response(pe.id, null, "UNKNOWN_ERROR", ex.toString()))
+                    exceptionRegistry.classCodes[ex::class]?.let { code ->
+                        sendPackage(Package.Response(pe.id, null, code, ex.toString()))
+                    } ?: run {
+                        ex.printStackTrace()
+                        sendPackage(Package.Response(pe.id, null, "UNKNOWN_ERROR", ex.toString()))
+                    }
                 }
             }
 
diff --git a/src/commonMain/kotlin/net.sergeych.parsec3/AdapterBuilder.kt b/src/commonMain/kotlin/net.sergeych.parsec3/AdapterBuilder.kt
index 8f13869..c36b547 100644
--- a/src/commonMain/kotlin/net.sergeych.parsec3/AdapterBuilder.kt
+++ b/src/commonMain/kotlin/net.sergeych.parsec3/AdapterBuilder.kt
@@ -5,11 +5,11 @@ import net.sergeych.mp_tools.globalLaunch
 
 class AdapterBuilder<S, H : CommandHost<S>>(
     val api: H,
-    private val exceptionRegistry: ExceptionsRegistry = ExceptionsRegistry(),
+    val exceptionRegistry: ExceptionsRegistry = ExceptionsRegistry(),
     f: AdapterBuilder<S, H>.() -> Unit,
 ) {
 
-    internal var sessionProducer: (suspend () -> S)? = null
+    internal var sessionProducer: (suspend () -> S) = { Unit as S}
         private set
 
 
@@ -24,15 +24,19 @@ class AdapterBuilder<S, H : CommandHost<S>>(
         api.on(ca, block)
     }
 
-    fun <T : Throwable> addError(code: String, handler: (String?) -> T) {
+    inline fun <reified T : Throwable> addError(code: String, noinline handler: (String?) -> T) {
         exceptionRegistry.register(code, handler)
     }
 
     suspend fun createWith(input: Flow<ByteArray>, f: suspend (ByteArray)->Unit ): Adapter<S> {
-        return Adapter<S>(sessionProducer!!(), api, exceptionRegistry) { f(it) }
+        return Adapter<S>(sessionProducer(), api, exceptionRegistry) { f(it) }
             .also { a-> globalLaunch { input.collect { a.receiveFrame(it)} } }
     }
 
+    suspend fun create(f: suspend (ByteArray) -> Unit): Adapter<S> {
+        return Adapter(sessionProducer(), api, exceptionRegistry, f)
+    }
+
     init {
         f(this)
     }
diff --git a/src/commonMain/kotlin/net.sergeych.parsec3/ExceptionsRegistry.kt b/src/commonMain/kotlin/net.sergeych.parsec3/ExceptionsRegistry.kt
index 018b518..fd86715 100644
--- a/src/commonMain/kotlin/net.sergeych.parsec3/ExceptionsRegistry.kt
+++ b/src/commonMain/kotlin/net.sergeych.parsec3/ExceptionsRegistry.kt
@@ -1,5 +1,7 @@
 package net.sergeych.parsec3
 
+import kotlin.reflect.KClass
+
 /**
  * Registry to restore exceptions from parsec block data. Serializing exceptions is dangerous: being a OS-bound
  * objects, exceptions can carry too much sensitive or useless information (e.g. call stack), and serializng
@@ -15,18 +17,21 @@ package net.sergeych.parsec3
  */
 open class ExceptionsRegistry {
 
-    private val handlers = mutableMapOf<String,(String?)->Throwable>().also {
+    val handlers = mutableMapOf<String,(String?)->Throwable>().also {
         // predefined exceptions:
         it[commandNotFoundCode] = { CommandNotFoundException(it ?: "???") }
         it[unknownErrorCode] = { UnknownException(it ?: "???") }
     }
 
+    val classCodes = mutableMapOf<KClass<*>,String>()
+
     /**
      * Register an exception with a code with a handler that creates its instance. Note that the
      * handler _should not throw anything_ but rather create an instance of the exception.
      */
-    fun <T: Throwable>register(code: String, block: (message: String?) -> T) {
+    inline fun <reified T: Throwable>register(code: String, noinline block: (message: String?) -> T) {
         handlers[code] = block
+        classCodes[T::class] = code
     }
 
     /**
diff --git a/src/commonMain/kotlin/net.sergeych.parsec3/Parsec3WSClient.kt b/src/commonMain/kotlin/net.sergeych.parsec3/Parsec3WSClient.kt
new file mode 100644
index 0000000..6f72e47
--- /dev/null
+++ b/src/commonMain/kotlin/net.sergeych.parsec3/Parsec3WSClient.kt
@@ -0,0 +1,66 @@
+package net.sergeych.parsec3
+
+import io.ktor.client.*
+import io.ktor.client.plugins.websocket.*
+import io.ktor.websocket.*
+import kotlinx.coroutines.CompletableDeferred
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.launch
+import net.sergeych.mp_logger.LogTag
+import net.sergeych.mp_logger.info
+import net.sergeych.mp_tools.globalLaunch
+
+class Parsec3WSClient<S, H : CommandHost<S>>(
+    val url: String,
+    val api: H,
+    val exceptionsRegistry: ExceptionsRegistry = ExceptionsRegistry(),
+    f: AdapterBuilder<S, H>.() -> Unit,
+) : LogTag("P3WSC") {
+
+    val builder = AdapterBuilder(api, exceptionsRegistry, f)
+
+    private val _connectionFlow = MutableStateFlow(false)
+    private val closeFlow = MutableStateFlow(false)
+    val connectedFlow: StateFlow<Boolean> = _connectionFlow
+
+
+    init {
+        start()
+    }
+
+    fun close() {
+        if( closeFlow.value == false ) closeFlow.value = true
+    }
+
+    var deferredAdapter = CompletableDeferred<Adapter<S>>()
+    private set
+
+    suspend fun adapter(): Adapter<S> = deferredAdapter.await()
+
+    fun start() {
+        globalLaunch {
+            client.webSocket(url) {
+                info { "Connected to $url" }
+                val a = builder.create { send(Frame.Binary(true, it)) }
+                _connectionFlow.value = true
+                launch { closeFlow.collect { if( it == true ) close() } }
+                deferredAdapter.complete(a)
+                for (f in incoming)
+                    if (f is Frame.Binary) a.receiveFrame(f.data)
+                // when we leave connection will be closed. So far we do not close the adapter,
+                // should we?
+                _connectionFlow.value = false
+                deferredAdapter = CompletableDeferred()
+            }
+        }
+    }
+
+    companion object {
+        private val client = HttpClient {
+            install(WebSockets) {
+                // Configure WebSockets
+            }
+        }
+    }
+}
diff --git a/src/commonTest/kotlin/parsec3/AdapterTest.kt b/src/commonTest/kotlin/parsec3/AdapterTest.kt
index c11efa9..485ad1a 100644
--- a/src/commonTest/kotlin/parsec3/AdapterTest.kt
+++ b/src/commonTest/kotlin/parsec3/AdapterTest.kt
@@ -56,6 +56,7 @@ internal class AdapterTest {
         // returns a string:
         val foo by command<String, String>()
         val ex by command<String,Unit>()
+        val ex2 by command<String,Unit>()
     }
     class ApiS2<T> : CommandHost<T>() {
         // create command `foo` that takes a string argument and
@@ -69,7 +70,7 @@ internal class AdapterTest {
         val ch21 = Channel<ByteArray>()
 
         val er = ExceptionsRegistry().also {
-            it.register("foo_x") { IllegalArgumentException("foo_x") }
+            it.register("foo_x") { IllegalArgumentException(it) }
         }
 
         val b1 = AdapterBuilder(ApiS1, er) {
@@ -78,7 +79,10 @@ internal class AdapterTest {
                 it + buzz + "foo"
             }
             on(ApiS1.ex) {
-                throw ParsecException("foo_x")
+                throw ParsecException("foo_x", it)
+            }
+            on(ApiS1.ex2) {
+                throw IllegalArgumentException()
             }
         }
         val b2 = AdapterBuilder(ApiS2<Unit>(), er) {
@@ -95,7 +99,9 @@ internal class AdapterTest {
         assertEquals("32142foo", a2.invokeCommand(ApiS1.foo, "321"))
 
         assertEquals("---42foo", ApiS1.foo.invoke(a2, "---"))
-        assertThrows<IllegalArgumentException> { ApiS1.ex.invoke(a2, "foobar") }
+        val x = assertThrows<IllegalArgumentException> { ApiS1.ex.invoke(a2, "foobar") }
+        assertEquals("foobar", x.message)
+        assertThrows<IllegalArgumentException> { ApiS1.ex2.invoke(a2, "foobar") }
 
         ch12.cancel()
         ch21.cancel()
diff --git a/src/jvmMain/kotlin/net/sergeych/parsec3/WsServer.kt b/src/jvmMain/kotlin/net/sergeych/parsec3/WsServer.kt
new file mode 100644
index 0000000..800b789
--- /dev/null
+++ b/src/jvmMain/kotlin/net/sergeych/parsec3/WsServer.kt
@@ -0,0 +1,47 @@
+package net.sergeych.parsec3
+
+import io.ktor.server.application.*
+import io.ktor.server.routing.*
+import io.ktor.server.websocket.*
+import io.ktor.websocket.*
+import net.sergeych.mp_logger.LogTag
+import net.sergeych.mp_logger.warning
+import java.time.Duration
+import java.util.concurrent.atomic.AtomicInteger
+import java.util.concurrent.atomic.AtomicLong
+
+fun <S, H : CommandHost<S>>Application.parsec3Server(
+    api: H,
+    exceptionsRegistry: ExceptionsRegistry = ExceptionsRegistry(),
+    path: String = "/api/p3",
+    f: AdapterBuilder<S, H>.() -> Unit,
+) {
+    val log = LogTag("P3WSS")
+    install(WebSockets) {
+        pingPeriod = Duration.ofSeconds(45)
+        timeout = Duration.ofSeconds(15)
+        maxFrameSize = Long.MAX_VALUE
+        masking = false
+    }
+
+    val builder = AdapterBuilder(api, exceptionsRegistry, f)
+
+    routing {
+        webSocket(path) { // websocketSession
+            val adapter = builder.create { outgoing.send(Frame.Binary(true, it)) }
+            for (frame in incoming) {
+                when (frame) {
+                    is Frame.Binary -> {
+                        adapter.receiveFrame(frame.readBytes())
+                    }
+                    else -> {
+                        log.warning { "unsupported frame type: $frame" }
+                    }
+                }
+            }
+        }
+        var totalConnections = AtomicLong(0)
+        var activeConnections = AtomicInteger(0)
+
+    }
+}
\ No newline at end of file
diff --git a/src/jvmTest/kotlin/net/sergeych/parsec3/WsServerKtTest.kt b/src/jvmTest/kotlin/net/sergeych/parsec3/WsServerKtTest.kt
new file mode 100644
index 0000000..a04e43c
--- /dev/null
+++ b/src/jvmTest/kotlin/net/sergeych/parsec3/WsServerKtTest.kt
@@ -0,0 +1,46 @@
+package net.sergeych.parsec3
+
+import io.ktor.server.engine.*
+import io.ktor.server.netty.*
+import kotlinx.coroutines.runBlocking
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+internal class WsServerKtTest {
+
+    data class TestSession(var buzz: String = "BuZZ")
+
+    object TestApiServer: CommandHost<TestSession>() {
+        val foo by command<String,String>()
+    }
+    object TestApiClient: CommandHost<Unit>() {
+        val bar by command<String,String>()
+    }
+
+    @Test
+    fun testWsServer() {
+
+        embeddedServer(Netty, port = 8080) {
+            parsec3Server(
+                TestApiServer,
+            ) {
+                newSession { TestSession() }
+                on(api.foo) {
+                    it + buzz + "-foo"
+                }
+            }
+        }.start(wait = false)
+
+        val client = Parsec3WSClient("ws://localhost:8080/api/p3", TestApiClient) {
+            on(api.bar) {
+                "bar:$it"
+            }
+        }
+        runBlocking {
+            val x = TestApiServer.foo.invoke(client.adapter(), "*great*")
+            assertEquals("*great*BuZZ-foo", x)
+            client.close()
+        }
+
+    }
+}
\ No newline at end of file