initial work on associated stream

still require testing, and fixing a few kinks:
- sending packets > 16k truncate them
- send one more packet than it could at eos
- probably update documentation

/!\ contains breaking changes

8 files changed, 382 insertions, 83 deletions

diff --git a/Cargo.lock b/Cargo.lock
index fe2a29d..356c3ba 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -153,12 +153,25 @@ dependencies = [
 
 [[package]]
 name = "env_logger"
+version = "0.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44533bbbb3bb3c1fa17d9f2e4e38bbbaf8396ba82193c4cb1b6445d711445d36"
+dependencies = [
+ "atty",
+ "humantime 1.3.0",
+ "log",
+ "regex",
+ "termcolor",
+]
+
+[[package]]
+name = "env_logger"
 version = "0.8.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a19187fea3ac7e84da7dacf48de0c45d63c6a76f9490dae389aead16c243fce3"
 dependencies = [
  "atty",
- "humantime",
+ "humantime 2.1.0",
  "log",
  "regex",
  "termcolor",
@@ -324,6 +337,15 @@ checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
 [[package]]
 name = "humantime"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df004cfca50ef23c36850aaaa59ad52cc70d0e90243c3c7737a4dd32dc7a3c4f"
+dependencies = [
+ "quick-error",
+]
+
+[[package]]
+name = "humantime"
 version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
@@ -440,7 +462,7 @@ dependencies = [
  "bytes 0.6.0",
  "cfg-if",
  "chrono",
- "env_logger",
+ "env_logger 0.8.4",
  "err-derive",
  "futures",
  "hex",
@@ -450,6 +472,8 @@ dependencies = [
  "lru",
  "opentelemetry",
  "opentelemetry-contrib",
+ "pin-project",
+ "pretty_env_logger",
  "rand 0.5.6",
  "rmp-serde",
  "serde",
@@ -583,6 +607,16 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "eb9f9e6e233e5c4a35559a617bf40a4ec447db2e84c20b55a6f83167b7e57872"
 
 [[package]]
+name = "pretty_env_logger"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "926d36b9553851b8b0005f1275891b392ee4d2d833852c417ed025477350fb9d"
+dependencies = [
+ "env_logger 0.7.1",
+ "log",
+]
+
+[[package]]
 name = "proc-macro-error"
 version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -628,6 +662,12 @@ dependencies = [
 ]
 
 [[package]]
+name = "quick-error"
+version = "1.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0"
+
+[[package]]
 name = "quote"
 version = "1.0.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/Cargo.toml b/Cargo.toml
index 536a1e6..a2f0ab1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -21,6 +21,7 @@ telemetry = ["opentelemetry", "opentelemetry-contrib", "rand"]
 
 [dependencies]
 futures = "0.3.17"
+pin-project = "1.0.10"
 tokio = { version = "1.0", default-features = false, features = ["net", "rt", "rt-multi-thread", "sync", "time", "macros", "io-util", "signal"] }
 tokio-util = { version = "0.6.8", default-features = false, features = ["compat"] }
 tokio-stream = "0.1.7"
@@ -47,6 +48,7 @@ opentelemetry-contrib = { version = "0.9", optional = true }
 
 [dev-dependencies]
 env_logger = "0.8"
+pretty_env_logger = "0.4"
 structopt = { version = "0.3", default-features = false }
 chrono = "0.4"
 
diff --git a/src/client.rs b/src/client.rs
index 8227e8f..bce7aca 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -37,10 +37,10 @@ pub(crate) struct ClientConn {
 	pub(crate) remote_addr: SocketAddr,
 	pub(crate) peer_id: NodeID,
 
-	query_send: ArcSwapOption<mpsc::UnboundedSender<(RequestID, RequestPriority, Vec<u8>)>>,
+	query_send: ArcSwapOption<mpsc::UnboundedSender<(RequestID, RequestPriority, Data)>>,
 
 	next_query_number: AtomicU32,
-	inflight: Mutex<HashMap<RequestID, oneshot::Sender<Vec<u8>>>>,
+	inflight: Mutex<HashMap<RequestID, oneshot::Sender<(Vec<u8>, AssociatedStream)>>>,
 }
 
 impl ClientConn {
@@ -148,9 +148,11 @@ impl ClientConn {
 	{
 		let query_send = self.query_send.load_full().ok_or(Error::ConnectionClosed)?;
 
+		// increment by 2; even are direct data; odd are associated stream
 		let id = self
 			.next_query_number
-			.fetch_add(1, atomic::Ordering::Relaxed);
+			.fetch_add(2, atomic::Ordering::Relaxed);
+		let stream_id = id + 1;
 
 		cfg_if::cfg_if! {
 			if #[cfg(feature = "telemetry")] {
@@ -166,7 +168,7 @@ impl ClientConn {
 		};
 
 		// Encode request
-		let body = rmp_to_vec_all_named(rq.borrow())?;
+		let (body, stream) = rmp_to_vec_all_named(rq.borrow())?;
 		drop(rq);
 
 		let request = QueryMessage {
@@ -185,7 +187,10 @@ impl ClientConn {
 			error!(
 				"Too many inflight requests! RequestID collision. Interrupting previous request."
 			);
-			if old_ch.send(vec![]).is_err() {
+			if old_ch
+				.send((vec![], Box::pin(futures::stream::empty())))
+				.is_err()
+			{
 				debug!("Could not send empty response to collisionned request, probably because request was interrupted. Dropping response.");
 			}
 		}
@@ -195,15 +200,20 @@ impl ClientConn {
 		#[cfg(feature = "telemetry")]
 		span.set_attribute(KeyValue::new("len_query", bytes.len() as i64));
 
-		query_send.send((id, prio, bytes))?;
+		query_send.send((id, prio, Data::Full(bytes)))?;
+		if let Some(stream) = stream {
+			query_send.send((stream_id, prio | PRIO_SECONDARY, Data::Streaming(stream)))?;
+		} else {
+			query_send.send((stream_id, prio, Data::Full(Vec::new())))?;
+		}
 
 		cfg_if::cfg_if! {
 			if #[cfg(feature = "telemetry")] {
-				let resp = resp_recv
+				let (resp, stream) = resp_recv
 					.with_context(Context::current_with_span(span))
 					.await?;
 			} else {
-				let resp = resp_recv.await?;
+				let (resp, stream) = resp_recv.await?;
 			}
 		}
 
@@ -217,10 +227,9 @@ impl ClientConn {
 
 		let code = resp[0];
 		if code == 0 {
-			Ok(rmp_serde::decode::from_read_ref::<
-				_,
-				<T as Message>::Response,
-			>(&resp[1..])?)
+			let mut deser = rmp_serde::decode::Deserializer::from_read_ref(&resp[1..]);
+			let res = T::Response::deserialize_msg(&mut deser, stream).await?;
+			Ok(res)
 		} else {
 			let msg = String::from_utf8(resp[1..].to_vec()).unwrap_or_default();
 			Err(Error::Remote(code, msg))
@@ -232,12 +241,12 @@ impl SendLoop for ClientConn {}
 
 #[async_trait]
 impl RecvLoop for ClientConn {
-	fn recv_handler(self: &Arc<Self>, id: RequestID, msg: Vec<u8>) {
+	fn recv_handler(self: &Arc<Self>, id: RequestID, msg: Vec<u8>, stream: AssociatedStream) {
 		trace!("ClientConn recv_handler {} ({} bytes)", id, msg.len());
 
 		let mut inflight = self.inflight.lock().unwrap();
 		if let Some(ch) = inflight.remove(&id) {
-			if ch.send(msg).is_err() {
+			if ch.send((msg, stream)).is_err() {
 				debug!("Could not send request response, probably because request was interrupted. Dropping response.");
 			}
 		}
diff --git a/src/endpoint.rs b/src/endpoint.rs
index 42e9a98..81ed036 100644
--- a/src/endpoint.rs
+++ b/src/endpoint.rs
@@ -5,7 +5,8 @@ use std::sync::Arc;
 use arc_swap::ArcSwapOption;
 use async_trait::async_trait;
 
-use serde::{Deserialize, Serialize};
+use serde::de::Error as DeError;
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
 
 use crate::error::Error;
 use crate::netapp::*;
@@ -14,8 +15,50 @@ use crate::util::*;
 
 /// This trait should be implemented by all messages your application
 /// wants to handle
-pub trait Message: Serialize + for<'de> Deserialize<'de> + Send + Sync {
-	type Response: Serialize + for<'de> Deserialize<'de> + Send + Sync;
+pub trait Message: SerializeMessage + Send + Sync {
+	type Response: SerializeMessage + Send + Sync;
+}
+
+/// A trait for de/serializing messages, with possible associated stream.
+#[async_trait]
+pub trait SerializeMessage: Sized {
+	fn serialize_msg<S: Serializer>(
+		&self,
+		serializer: S,
+	) -> Result<(S::Ok, Option<AssociatedStream>), S::Error>;
+
+	async fn deserialize_msg<'de, D: Deserializer<'de> + Send>(
+		deserializer: D,
+		stream: AssociatedStream,
+	) -> Result<Self, D::Error>;
+}
+
+#[async_trait]
+impl<T> SerializeMessage for T
+where
+	T: Serialize + for<'de> Deserialize<'de> + Send + Sync,
+{
+	fn serialize_msg<S: Serializer>(
+		&self,
+		serializer: S,
+	) -> Result<(S::Ok, Option<AssociatedStream>), S::Error> {
+		self.serialize(serializer).map(|r| (r, None))
+	}
+
+	async fn deserialize_msg<'de, D: Deserializer<'de> + Send>(
+		deserializer: D,
+		mut stream: AssociatedStream,
+	) -> Result<Self, D::Error> {
+		use futures::StreamExt;
+
+		let res = Self::deserialize(deserializer)?;
+		if stream.next().await.is_some() {
+			return Err(D::Error::custom(
+				"failed to deserialize: found associated stream when none expected",
+			));
+		}
+		Ok(res)
+	}
 }
 
 /// This trait should be implemented by an object of your application
@@ -128,7 +171,12 @@ pub(crate) type DynEndpoint = Box<dyn GenericEndpoint + Send + Sync>;
 
 #[async_trait]
 pub(crate) trait GenericEndpoint {
-	async fn handle(&self, buf: &[u8], from: NodeID) -> Result<Vec<u8>, Error>;
+	async fn handle(
+		&self,
+		buf: &[u8],
+		stream: AssociatedStream,
+		from: NodeID,
+	) -> Result<(Vec<u8>, Option<AssociatedStream>), Error>;
 	fn drop_handler(&self);
 	fn clone_endpoint(&self) -> DynEndpoint;
 }
@@ -145,11 +193,17 @@ where
 	M: Message + 'static,
 	H: EndpointHandler<M> + 'static,
 {
-	async fn handle(&self, buf: &[u8], from: NodeID) -> Result<Vec<u8>, Error> {
+	async fn handle(
+		&self,
+		buf: &[u8],
+		stream: AssociatedStream,
+		from: NodeID,
+	) -> Result<(Vec<u8>, Option<AssociatedStream>), Error> {
 		match self.0.handler.load_full() {
 			None => Err(Error::NoHandler),
 			Some(h) => {
-				let req = rmp_serde::decode::from_read_ref::<_, M>(buf)?;
+				let mut deser = rmp_serde::decode::Deserializer::from_read_ref(buf);
+				let req = M::deserialize_msg(&mut deser, stream).await?;
 				let res = h.handle(&req, from).await;
 				let res_bytes = rmp_to_vec_all_named(&res)?;
 				Ok(res_bytes)
diff --git a/src/proto.rs b/src/proto.rs
index e843bff..b45ff13 100644
--- a/src/proto.rs
+++ b/src/proto.rs
@@ -1,9 +1,13 @@
 use std::collections::{HashMap, VecDeque};
+use std::pin::Pin;
 use std::sync::Arc;
+use std::task::{Context, Poll};
 
-use log::trace;
+use log::{trace, warn};
 
-use futures::{AsyncReadExt, AsyncWriteExt};
+use futures::channel::mpsc::{unbounded, UnboundedReceiver, UnboundedSender};
+use futures::Stream;
+use futures::{AsyncReadExt, AsyncWriteExt, FutureExt, StreamExt};
 use kuska_handshake::async_std::BoxStreamWrite;
 
 use tokio::sync::mpsc;
@@ -11,6 +15,7 @@ use tokio::sync::mpsc;
 use async_trait::async_trait;
 
 use crate::error::*;
+use crate::util::AssociatedStream;
 
 /// Priority of a request (click to read more about priorities).
 ///
@@ -48,14 +53,73 @@ pub const PRIO_SECONDARY: RequestPriority = 0x01;
 
 pub(crate) type RequestID = u32;
 type ChunkLength = u16;
-const MAX_CHUNK_LENGTH: ChunkLength = 0x4000;
+pub(crate) const MAX_CHUNK_LENGTH: ChunkLength = 0x4000;
 const CHUNK_HAS_CONTINUATION: ChunkLength = 0x8000;
 
 struct SendQueueItem {
 	id: RequestID,
 	prio: RequestPriority,
-	data: Vec<u8>,
-	cursor: usize,
+	data: DataReader,
+}
+
+pub(crate) enum Data {
+	Full(Vec<u8>),
+	Streaming(AssociatedStream),
+}
+
+#[pin_project::pin_project(project = DataReaderProj)]
+enum DataReader {
+	Full {
+		#[pin]
+		data: Vec<u8>,
+		pos: usize,
+	},
+	Streaming {
+		#[pin]
+		reader: AssociatedStream,
+	},
+}
+
+impl From<Data> for DataReader {
+	fn from(data: Data) -> DataReader {
+		match data {
+			Data::Full(data) => DataReader::Full { data, pos: 0 },
+			Data::Streaming(reader) => DataReader::Streaming { reader },
+		}
+	}
+}
+
+impl Stream for DataReader {
+	type Item = ([u8; MAX_CHUNK_LENGTH as usize], usize);
+
+	fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+		match self.project() {
+			DataReaderProj::Full { data, pos } => {
+				let len = std::cmp::min(MAX_CHUNK_LENGTH as usize, data.len() - *pos);
+				let end = *pos + len;
+
+				if len == 0 {
+					Poll::Ready(None)
+				} else {
+					let mut body = [0; MAX_CHUNK_LENGTH as usize];
+					body[..len].copy_from_slice(&data[*pos..end]);
+					*pos = end;
+					Poll::Ready(Some((body, len)))
+				}
+			}
+			DataReaderProj::Streaming { reader } => {
+				reader.poll_next(cx).map(|opt| {
+					opt.map(|v| {
+						let mut body = [0; MAX_CHUNK_LENGTH as usize];
+						let len = std::cmp::min(MAX_CHUNK_LENGTH as usize, v.len());
+						// TODO this can throw away long vec, they should be splited instead
+						body[..len].copy_from_slice(&v[..len]);
+						(body, len)
+					})
+				})
+			}
+		}
+	}
 }
 
 struct SendQueue {
@@ -108,7 +172,7 @@ impl SendQueue {
 pub(crate) trait SendLoop: Sync {
 	async fn send_loop<W>(
 		self: Arc<Self>,
-		mut msg_recv: mpsc::UnboundedReceiver<(RequestID, RequestPriority, Vec<u8>)>,
+		mut msg_recv: mpsc::UnboundedReceiver<(RequestID, RequestPriority, Data)>,
 		mut write: BoxStreamWrite<W>,
 	) -> Result<(), Error>
 	where
@@ -118,51 +182,78 @@ pub(crate) trait SendLoop: Sync {
 		let mut should_exit = false;
 		while !should_exit || !sending.is_empty() {
 			if let Ok((id, prio, data)) = msg_recv.try_recv() {
-				trace!("send_loop: got {}, {} bytes", id, data.len());
+				match &data {
+					Data::Full(data) => {
+						trace!("send_loop: got {}, {} bytes", id, data.len());
+					}
+					Data::Streaming(_) => {
+						trace!("send_loop: got {}, unknown size", id);
+					}
+				}
 				sending.push(SendQueueItem {
 					id,
 					prio,
-					data,
-					cursor: 0,
+					data: data.into(),
 				});
 			} else if let Some(mut item) = sending.pop() {
 				trace!(
-					"send_loop: sending bytes for {} ({} bytes, {} already sent)",
-					item.id,
-					item.data.len(),
-					item.cursor
+					"send_loop: sending bytes for {}",
+                    item.id,
 				);
+
+				let data = futures::select! {
+					data = item.data.next().fuse() => data,
+					default => {
+						// nothing to send yet; re-schedule and find something else to do
+						sending.push(item);
+						continue;
+
+						// TODO if every SendQueueItem is waiting on data, use select_all to await
+						// something to do
+						// TODO find some way to not require sending empty last chunk
+					}
+				};
+
 				let header_id = RequestID::to_be_bytes(item.id);
 				write.write_all(&header_id[..]).await?;
 
-				if item.data.len() - item.cursor > MAX_CHUNK_LENGTH as usize {
+				let data = match data.as_ref() {
+					Some((data, len)) => &data[..*len],
+					None => &[],
+				};
+
+				if !data.is_empty() {
 					let size_header =
-						ChunkLength::to_be_bytes(MAX_CHUNK_LENGTH | CHUNK_HAS_CONTINUATION);
+						ChunkLength::to_be_bytes(data.len() as u16 | CHUNK_HAS_CONTINUATION);
 					write.write_all(&size_header[..]).await?;
 
-					let new_cursor = item.cursor + MAX_CHUNK_LENGTH as usize;
-					write.write_all(&item.data[item.cursor..new_cursor]).await?;
-					item.cursor = new_cursor;
+					write.write_all(data).await?;
 
 					sending.push(item);
 				} else {
-					let send_len = (item.data.len() - item.cursor) as ChunkLength;
-
-					let size_header = ChunkLength::to_be_bytes(send_len);
+					// this is always zero for now, but may be more when above TODO get fixed
+					let size_header = ChunkLength::to_be_bytes(data.len() as u16);
 					write.write_all(&size_header[..]).await?;
 
-					write.write_all(&item.data[item.cursor..]).await?;
+					write.write_all(data).await?;
 				}
+
 				write.flush().await?;
 			} else {
 				let sth = msg_recv.recv().await;
 				if let Some((id, prio, data)) = sth {
-					trace!("send_loop: got {}, {} bytes", id, data.len());
+					match &data {
+						Data::Full(data) => {
+							trace!("send_loop: got {}, {} bytes", id, data.len());
+						}
+						Data::Streaming(_) => {
+							trace!("send_loop: got {}, unknown size", id);
+						}
+					}
 					sending.push(SendQueueItem {
 						id,
 						prio,
-						data,
-						cursor: 0,
+						data: data.into(),
 					});
 				} else {
 					should_exit = true;
@@ -175,6 +266,41 @@ pub(crate) trait SendLoop: Sync {
 	}
 }
 
+struct ChannelPair {
+        receiver: Option<UnboundedReceiver<Vec<u8>>>,
+        sender: Option<UnboundedSender<Vec<u8>>>,
+}
+
+impl ChannelPair {
+    fn take_receiver(&mut self) -> Option<UnboundedReceiver<Vec<u8>>> {
+        self.receiver.take()
+    }
+
+    fn take_sender(&mut self) -> Option<UnboundedSender<Vec<u8>>> {
+        self.sender.take()
+    }
+
+    fn ref_sender(&mut self) -> Option<&UnboundedSender<Vec<u8>>> {
+        self.sender.as_ref().take()
+    }
+
+    fn insert_into(self, map: &mut HashMap<RequestID, ChannelPair>, index: RequestID) {
+        if self.receiver.is_some() || self.sender.is_some() {
+            map.insert(index, self);
+        }
+    }
+}
+
+impl Default for ChannelPair {
+    fn default() -> Self {
+        let (send, recv) = unbounded();
+        ChannelPair {
+            receiver: Some(recv),
+            sender: Some(send),
+        }
+    }
+}
+
 /// The RecvLoop trait, which is implemented both by the client and the server
 /// connection objects (ServerConn and ClientConn) adds a method `.recv_loop()`
 /// and a prototype of a handler for received messages `.recv_handler()` that
@@ -184,13 +310,17 @@ pub(crate) trait SendLoop: Sync {
 /// the full message is passed to the receive handler.
 #[async_trait]
 pub(crate) trait RecvLoop: Sync + 'static {
-	fn recv_handler(self: &Arc<Self>, id: RequestID, msg: Vec<u8>);
+	fn recv_handler(self: &Arc<Self>, id: RequestID, msg: Vec<u8>, stream: AssociatedStream);
 
 	async fn recv_loop<R>(self: Arc<Self>, mut read: R) -> Result<(), Error>
 	where
 		R: AsyncReadExt + Unpin + Send + Sync,
 	{
-		let mut receiving = HashMap::new();
+		let mut receiving: HashMap<RequestID, Vec<u8>> = HashMap::new();
+		let mut streams: HashMap<
+			RequestID,
+            ChannelPair,
+		> = HashMap::new();
 		loop {
 			trace!("recv_loop: reading packet");
 			let mut header_id = [0u8; RequestID::BITS as usize / 8];
@@ -214,13 +344,43 @@ pub(crate) trait RecvLoop: Sync + 'static {
 			read.read_exact(&mut next_slice[..]).await?;
 			trace!("recv_loop: read {} bytes", next_slice.len());
 
-			let mut msg_bytes: Vec<_> = receiving.remove(&id).unwrap_or_default();
-			msg_bytes.extend_from_slice(&next_slice[..]);
+			if id & 1 == 0 {
+                // main stream
+				let mut msg_bytes = receiving.remove(&id).unwrap_or_default();
+				msg_bytes.extend_from_slice(&next_slice[..]);
 
-			if has_cont {
-				receiving.insert(id, msg_bytes);
+				if has_cont {
+					receiving.insert(id, msg_bytes);
+				} else {
+					let mut channel_pair = streams.remove(&(id | 1)).unwrap_or_default();
+
+					if let Some(receiver) = channel_pair.take_receiver() {
+						self.recv_handler(id, msg_bytes, Box::pin(receiver));
+					} else {
+                        warn!("Couldn't take receiver part of stream")
+                    }
+
+                    channel_pair.insert_into(&mut streams, id | 1);
+				}
 			} else {
-				self.recv_handler(id, msg_bytes);
+                // associated stream
+                let mut channel_pair = streams.remove(&(id)).unwrap_or_default();
+
+				// if we get an error, the receiving end is disconnected. We still need to
+				// reach eos before dropping this sender
+                if !next_slice.is_empty() {
+                    if let Some(sender) = channel_pair.ref_sender() {
+                        let _ = sender.unbounded_send(next_slice);
+                    } else {
+                        warn!("Couldn't take sending part of stream")
+                    }
+                }
+
+				if !has_cont {
+                    channel_pair.take_sender();
+                }
+
+                channel_pair.insert_into(&mut streams, id);
 			}
 		}
 		Ok(())
@@ -236,38 +396,50 @@ mod test {
 		let i1 = SendQueueItem {
 			id: 1,
 			prio: PRIO_NORMAL,
-			data: vec![],
-			cursor: 0,
+			data: DataReader::Full {
+				data: vec![],
+				pos: 0,
+			},
 		};
 		let i2 = SendQueueItem {
 			id: 2,
 			prio: PRIO_HIGH,
-			data: vec![],
-			cursor: 0,
+			data: DataReader::Full {
+				data: vec![],
+				pos: 0,
+			},
 		};
 		let i2bis = SendQueueItem {
 			id: 20,
 			prio: PRIO_HIGH,
-			data: vec![],
-			cursor: 0,
+			data: DataReader::Full {
+				data: vec![],
+				pos: 0,
+			},
 		};
 		let i3 = SendQueueItem {
 			id: 3,
 			prio: PRIO_HIGH | PRIO_SECONDARY,
-			data: vec![],
-			cursor: 0,
+			data: DataReader::Full {
+				data: vec![],
+				pos: 0,
+			},
 		};
 		let i4 = SendQueueItem {
 			id: 4,
 			prio: PRIO_BACKGROUND | PRIO_SECONDARY,
-			data: vec![],
-			cursor: 0,
+			data: DataReader::Full {
+				data: vec![],
+				pos: 0,
+			},
 		};
 		let i5 = SendQueueItem {
 			id: 5,
 			prio: PRIO_BACKGROUND | PRIO_PRIMARY,
-			data: vec![],
-			cursor: 0,
+			data: DataReader::Full {
+				data: vec![],
+				pos: 0,
+			},
 		};
 
 		let mut q = SendQueue::new();
diff --git a/src/server.rs b/src/server.rs
index 5465307..6cd4056 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -55,7 +55,7 @@ pub(crate) struct ServerConn {
 
 	netapp: Arc<NetApp>,
 
-	resp_send: ArcSwapOption<mpsc::UnboundedSender<(RequestID, RequestPriority, Vec<u8>)>>,
+	resp_send: ArcSwapOption<mpsc::UnboundedSender<(RequestID, RequestPriority, Data)>>,
 }
 
 impl ServerConn {
@@ -123,7 +123,11 @@ impl ServerConn {
 		Ok(())
 	}
 
-	async fn recv_handler_aux(self: &Arc<Self>, bytes: &[u8]) -> Result<Vec<u8>, Error> {
+	async fn recv_handler_aux(
+		self: &Arc<Self>,
+		bytes: &[u8],
+		stream: AssociatedStream,
+	) -> Result<(Vec<u8>, Option<AssociatedStream>), Error> {
 		let msg = QueryMessage::decode(bytes)?;
 		let path = String::from_utf8(msg.path.to_vec())?;
 
@@ -156,11 +160,11 @@ impl ServerConn {
 					span.set_attribute(KeyValue::new("path", path.to_string()));
 					span.set_attribute(KeyValue::new("len_query", msg.body.len() as i64));
 
-					handler.handle(msg.body, self.peer_id)
+					handler.handle(msg.body, stream, self.peer_id)
 						.with_context(Context::current_with_span(span))
 						.await
 				} else {
-					handler.handle(msg.body, self.peer_id).await
+					handler.handle(msg.body, stream, self.peer_id).await
 				}
 			}
 		} else {
@@ -173,7 +177,7 @@ impl SendLoop for ServerConn {}
 
 #[async_trait]
 impl RecvLoop for ServerConn {
-	fn recv_handler(self: &Arc<Self>, id: RequestID, bytes: Vec<u8>) {
+	fn recv_handler(self: &Arc<Self>, id: RequestID, bytes: Vec<u8>, stream: AssociatedStream) {
 		let resp_send = self.resp_send.load_full().unwrap();
 
 		let self2 = self.clone();
@@ -182,26 +186,36 @@ impl RecvLoop for ServerConn {
 			let bytes: Bytes = bytes.into();
 
 			let prio = if !bytes.is_empty() { bytes[0] } else { 0u8 };
-			let resp = self2.recv_handler_aux(&bytes[..]).await;
+			let resp = self2.recv_handler_aux(&bytes[..], stream).await;
 
-			let resp_bytes = match resp {
-				Ok(rb) => {
+			let (resp_bytes, resp_stream) = match resp {
+				Ok((rb, rs)) => {
 					let mut resp_bytes = vec![0u8];
 					resp_bytes.extend(rb);
-					resp_bytes
+					(resp_bytes, rs)
 				}
 				Err(e) => {
 					let mut resp_bytes = vec![e.code()];
 					resp_bytes.extend(e.to_string().into_bytes());
-					resp_bytes
+					(resp_bytes, None)
 				}
 			};
 
 			trace!("ServerConn sending response to {}: ", id);
 
 			resp_send
-				.send((id, prio, resp_bytes))
-				.log_err("ServerConn recv_handler send resp");
+				.send((id, prio, Data::Full(resp_bytes)))
+				.log_err("ServerConn recv_handler send resp bytes");
+
+			if let Some(resp_stream) = resp_stream {
+				resp_send
+					.send((id + 1, prio, Data::Streaming(resp_stream)))
+					.log_err("ServerConn recv_handler send resp stream");
+			} else {
+				resp_send
+					.send((id + 1, prio, Data::Full(Vec::new())))
+					.log_err("ServerConn recv_handler send resp stream");
+			}
 		});
 	}
 }
diff --git a/src/test.rs b/src/test.rs
index 82c7ba6..ecd5450 100644
--- a/src/test.rs
+++ b/src/test.rs
@@ -14,6 +14,7 @@ use crate::NodeID;
 
 #[tokio::test(flavor = "current_thread")]
 async fn test_with_basic_scheduler() {
+	pretty_env_logger::init();
 	run_test().await
 }
 
diff --git a/src/util.rs b/src/util.rs
index f4dfac7..4333080 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -1,7 +1,10 @@
+use crate::endpoint::SerializeMessage;
+
 use std::net::SocketAddr;
 use std::net::ToSocketAddrs;
+use std::pin::Pin;
 
-use serde::Serialize;
+use futures::Stream;
 
 use log::info;
 
@@ -14,21 +17,25 @@ pub type NodeKey = sodiumoxide::crypto::sign::ed25519::SecretKey;
 /// A network key
 pub type NetworkKey = sodiumoxide::crypto::auth::Key;
 
+pub type AssociatedStream = Pin<Box<dyn Stream<Item = Vec<u8>> + Send>>;
+
 /// Utility function: encodes any serializable value in MessagePack binary format
 /// using the RMP library.
 ///
 /// Field names and variant names are included in the serialization.
 /// This is used internally by the netapp communication protocol.
-pub fn rmp_to_vec_all_named<T>(val: &T) -> Result<Vec<u8>, rmp_serde::encode::Error>
+pub fn rmp_to_vec_all_named<T>(
+	val: &T,
+) -> Result<(Vec<u8>, Option<AssociatedStream>), rmp_serde::encode::Error>
 where
-	T: Serialize + ?Sized,
+	T: SerializeMessage + ?Sized,
 {
 	let mut wr = Vec::with_capacity(128);
 	let mut se = rmp_serde::Serializer::new(&mut wr)
 		.with_struct_map()
 		.with_string_variants();
-	val.serialize(&mut se)?;
-	Ok(wr)
+	let (_, stream) = val.serialize_msg(&mut se)?;
+	Ok((wr, stream))
 }
 
 /// This async function returns only when a true signal was received