diff --git a/hptp-send/src/main.rs b/hptp-send/src/main.rs
index 4bd39ea..e9ffbc8 100644
--- a/hptp-send/src/main.rs
+++ b/hptp-send/src/main.rs
@@ -91,36 +91,34 @@ async fn send(peer: &mut Peer, m: Msg) -> Result<(), Error> {
     }
 }
 
-async fn recv(log: &mut Logger, peer: &mut Peer) -> Result<Option<Msg>, Error> {
-    match peer.recv().await {
-        Ok(m) => Ok(Some(m)),
-        Err(peer::RecvError::Io { source }) => Err(source.into()),
-        Err(peer::RecvError::InvalidMessage { .. }) => {
-            log.recv_corrupt().await;
-            Ok(None)
-        }
-    }
-}
-
 async fn upload<IN>(log: &mut Logger, peer: &mut Peer, inp: &mut IN) -> Result<(), Error>
 where
     IN: AsyncRead + Unpin,
 {
     let mut pos = 0;
+    let mut next_ack_len: Option<usize> = None;
     loop {
-        match read_data(inp).await? {
-            Some(data) => {
-                let len = data.len();
-                send(peer, Msg::Data(data)).await?;
-                log.send_data(pos, len).await;
-                if let Some(Msg::Ack) = recv(log, peer).await? {
+        if let Some(ack_len) = next_ack_len {
+            match peer.recv().await {
+                Ok(Msg::Ack) => {
                     log.recv_ack(pos).await;
-                } else {
-                    log.debug_msg("didn't get ack??").await;
+                    pos += ack_len;
+                    next_ack_len = None;
                 }
-                pos += len;
+                Ok(_) => log.debug_msg("got some other packet??").await,
+
+                Err(peer::RecvError::InvalidMessage { .. }) => log.recv_corrupt().await,
+                Err(peer::RecvError::Io { source }) => return Err(source.into()),
+            }
+        } else {
+            match read_data(inp).await? {
+                Some(data) => {
+                    next_ack_len = Some(data.len());
+                    log.send_data(pos, data.len()).await;
+                    send(peer, Msg::Data(data)).await?;
+                }
+                None => break,
             }
-            None => break,
         }
     }
     log.completed().await;