diff --git a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeBuilder.kt b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeBuilder.kt
index b5a32590..0f12c213 100644
--- a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeBuilder.kt
+++ b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeBuilder.kt
@@ -1,7 +1,10 @@
 package hep.dataforge.io
 
 import hep.dataforge.meta.*
-import kotlinx.io.*
+import kotlinx.io.ArrayBinary
+import kotlinx.io.Binary
+import kotlinx.io.ExperimentalIoApi
+import kotlinx.io.Output
 
 class EnvelopeBuilder {
     private val metaBuilder = MetaBuilder()
@@ -26,9 +29,7 @@ class EnvelopeBuilder {
      */
     @ExperimentalIoApi
     fun data(block: Output.() -> Unit) {
-        val bytes = buildBytes(builder = block)
-        data = bytes.toByteArray().asBinary() //save data to byte array so
-        bytes.close()
+        data = ArrayBinary.write(builder = block)
     }
 
     internal fun build() = SimpleEnvelope(metaBuilder.seal(), data)
diff --git a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeParts.kt b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeParts.kt
index 471ee3be..8e0b16de 100644
--- a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeParts.kt
+++ b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/EnvelopeParts.kt
@@ -21,7 +21,7 @@ object EnvelopeParts {
     val FORMAT_NAME_KEY = Envelope.ENVELOPE_NODE_KEY + MULTIPART_KEY + "format"
     val FORMAT_META_KEY = Envelope.ENVELOPE_NODE_KEY + MULTIPART_KEY + "meta"
 
-    const val MULTIPART_DATA_SEPARATOR = "#~PART~#\r\n"
+    const val MULTIPART_DATA_SEPARATOR = "\r\n#~PART~#\r\n"
 
     const val MULTIPART_DATA_TYPE = "envelope.multipart"
 }
@@ -113,7 +113,7 @@ fun Envelope.parts(io: IOPlugin = Global.plugins.fetch(IOPlugin)): Sequence<Enve
                     sequence {
                         repeat(size) {
                             val separator = readRawString(MULTIPART_DATA_SEPARATOR.length)
-                            if(separator!= MULTIPART_DATA_SEPARATOR) error("Separator is expected")
+                            if(separator!= MULTIPART_DATA_SEPARATOR) error("Separator is expected, but $separator found")
                             yield(readObject())
                         }
                     }
diff --git a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaglessEnvelopeFormat.kt b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaglessEnvelopeFormat.kt
index 32787cf7..5b22ae8c 100644
--- a/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaglessEnvelopeFormat.kt
+++ b/dataforge-io/src/commonMain/kotlin/hep/dataforge/io/TaglessEnvelopeFormat.kt
@@ -106,9 +106,9 @@ class TaglessEnvelopeFormat(
             readArray(bytes)
             bytes.asBinary()
         } else {
-            buildBytes {
+            ArrayBinary.write {
                 writeInput(this@readObject)
-            }.toByteArray().asBinary()
+            }
         }
 
         return SimpleEnvelope(meta, data)
diff --git a/dataforge-io/src/commonTest/kotlin/hep/dataforge/io/MultipartTest.kt b/dataforge-io/src/commonTest/kotlin/hep/dataforge/io/MultipartTest.kt
index ae25df06..0f60c077 100644
--- a/dataforge-io/src/commonTest/kotlin/hep/dataforge/io/MultipartTest.kt
+++ b/dataforge-io/src/commonTest/kotlin/hep/dataforge/io/MultipartTest.kt
@@ -3,6 +3,7 @@ package hep.dataforge.io
 import hep.dataforge.meta.DFExperimental
 import hep.dataforge.meta.get
 import hep.dataforge.meta.int
+import kotlinx.io.text.writeRawString
 import kotlinx.io.text.writeUtf8String
 
 import kotlin.test.Test
@@ -18,9 +19,9 @@ class MultipartTest {
             }
             data {
                 writeUtf8String("Hello World $it")
-//                repeat(2000) {
-//                    writeInt(it)
-//                }
+                repeat(300) {
+                    writeRawString("$it ")
+                }
             }
         }
     }
diff --git a/dataforge-io/src/jvmMain/kotlin/hep/dataforge/io/tcp/EnvelopeClient.kt b/dataforge-io/src/jvmMain/kotlin/hep/dataforge/io/tcp/EnvelopeClient.kt
index 6c7e36c6..9562d146 100644
--- a/dataforge-io/src/jvmMain/kotlin/hep/dataforge/io/tcp/EnvelopeClient.kt
+++ b/dataforge-io/src/jvmMain/kotlin/hep/dataforge/io/tcp/EnvelopeClient.kt
@@ -38,7 +38,7 @@ class EnvelopeClient(
     suspend fun close() {
         try {
             respond(
-                Envelope.invoke {
+                Envelope {
                     type = EnvelopeServer.SHUTDOWN_ENVELOPE_TYPE
                 }
             )
diff --git a/dataforge-io/src/jvmMain/kotlin/hep/dataforge/io/tcp/EnvelopeServer.kt b/dataforge-io/src/jvmMain/kotlin/hep/dataforge/io/tcp/EnvelopeServer.kt
index 778e563f..10c5b712 100644
--- a/dataforge-io/src/jvmMain/kotlin/hep/dataforge/io/tcp/EnvelopeServer.kt
+++ b/dataforge-io/src/jvmMain/kotlin/hep/dataforge/io/tcp/EnvelopeServer.kt
@@ -78,6 +78,9 @@ class EnvelopeServer(
                     logger.debug { "Accepted request with type ${request.type} from ${socket.remoteSocketAddress}" }
                     if (request.type == SHUTDOWN_ENVELOPE_TYPE) {
                         //Echo shutdown command
+                        outputStream.write{
+                            writeObject(request)
+                        }
                         logger.info { "Accepted graceful shutdown signal from ${socket.inetAddress}" }
                         socket.close()
                         return@thread