diff --git a/src/buffers.rs b/src/buffers.rs
index 95a45c2..d468847 100644
--- a/src/buffers.rs
+++ b/src/buffers.rs
@@ -1,21 +1,34 @@
+use crate::CmdErr;
+use tokio::net::tcp::OwnedReadHalf;
+
 struct ReadState {
-    // rx: OwnedReadHalf,
     buffer: Vec<u8>,
-    cursor: usize,
+    read_cursor: usize,
+    write_cursor: usize,
 }
 
 impl ReadState {
+    fn new(len: usize) -> Self {
+        let buffer = vec![0; len];
+        Self {
+            buffer,
+            read_cursor: 0,
+            write_cursor: 0,
+        }
+    }
+
     fn has_next(&self) -> bool {
-        self.buffer[..self.cursor]
+        self.buffer[..self.read_cursor]
             .iter()
             .position(|v| *v == b'\n')
             .is_some()
     }
-    fn shift_ramaining(&mut self) {
+
+    fn shift_remaining(&mut self) {
         if !self.has_next() {
             return;
         }
-        let pos = self.cursor;
+        let pos = self.read_cursor;
         let mut last_old = 0;
         let mut last_new = 0;
         for (new, old) in (pos..self.buffer.len()).enumerate() {
@@ -33,32 +46,86 @@ impl ReadState {
             // eprintln!("erase {old}");
             self.buffer[old] = 0;
         }
-        self.cursor = 0;
+        self.read_cursor = 0;
+        self.write_cursor = self.buffer.iter().position(|n| *n == 0).unwrap_or_default();
     }
-    fn next(&mut self) -> Option<&[u8]> {
-        let Some(end) = self.buffer[self.cursor..self.buffer.len()]
+
+    fn next<'s>(&'s mut self) -> Option<&'s [u8]> {
+        let Some(end) = self.buffer[self.read_cursor..self.buffer.len()]
             .iter()
-            .position(|v| *v == b'\n').map(|n| n + self.cursor) else {
+            .position(|v| *v == b'\n').map(|n| n + self.read_cursor) else {
             return None;
         };
         // eprintln!("cursor {} end {end}", self.cursor);
-        let s = &self.buffer[self.cursor..=end];
-        self.cursor = (end + 1).min(self.buffer.len() - 1);
+        let s = &self.buffer[self.read_cursor..=end];
+        self.read_cursor = (end + 1).min(self.buffer.len());
         Some(s)
     }
+
+    fn write(&mut self, buffer: &[u8]) -> Result<usize, CmdErr> {
+        if self.write_cursor + buffer.len() > self.buffer.len() {
+            return Err(CmdErr::BufferFull);
+        }
+        let wc = self.write_cursor;
+        for (idx, b) in buffer.iter().copied().enumerate() {
+            self.buffer[idx + wc] = b;
+        }
+        self.write_cursor = wc + buffer.len();
+        Ok(self.write_cursor)
+    }
+}
+
+struct TcpReadState<'read, 'buffer> {
+    reader: &'read mut OwnedReadHalf,
+    buffer: &'buffer mut ReadState,
+}
+
+impl<'read, 'buffer> TcpReadState<'read, 'buffer> {
+    pub fn new(reader: &'read mut OwnedReadHalf, buffer: &'buffer mut ReadState) -> Self {
+        Self {
+            reader,
+            buffer,
+        }
+    }
+
+    pub async fn next(&mut self) -> Option<&'buffer [u8]> {
+        use tokio::io::AsyncReadExt;
+        use tracing::*;
+        {
+            if let Some(v) = self.buffer.next() {
+                return Some(v);
+            }
+        }
+
+        {
+            match self.reader.read_buf(&mut self.buffer.buffer).await {
+                Ok(n) => {
+                    debug!("received {n} bytes");
+                }
+                Err(e) => {
+                    debug!("Failed to read from rx: {e}");
+                    return None;
+                }
+            };
+        }
+        {
+            self.buffer.next()
+        }
+    }
 }
 
 #[cfg(test)]
-mod tests {
+mod read_test {
     use super::*;
 
     #[test]
     fn shift_empty() {
         let mut state = ReadState {
             buffer: vec![0, 0, 0, 0, 0, 0, 0, 0],
-            cursor: 0,
+            read_cursor: 0,
+            write_cursor: 0,
         };
-        state.shift_ramaining();
+        state.shift_remaining();
         let expected = vec![0, 0, 0, 0, 0, 0, 0, 0];
         assert_eq!(
             std::str::from_utf8(&state.buffer),
@@ -69,9 +136,10 @@ mod tests {
     fn shift_single_unterminated() {
         let mut state = ReadState {
             buffer: vec![b'h', b'e', b'l', b'l', b'o', 0, 0, 0],
-            cursor: 0,
+            read_cursor: 0,
+            write_cursor: 0,
         };
-        state.shift_ramaining();
+        state.shift_remaining();
         let expected = vec![b'h', b'e', b'l', b'l', b'o', 0, 0, 0];
         assert_eq!(
             std::str::from_utf8(&state.buffer),
@@ -82,9 +150,10 @@ mod tests {
     fn shift_single_terminated() {
         let mut state = ReadState {
             buffer: vec![b'h', b'e', b'l', b'l', b'o', b'\r', b'\n', 0],
-            cursor: 0,
+            read_cursor: 0,
+            write_cursor: 0,
         };
-        state.shift_ramaining();
+        state.shift_remaining();
         let expected = vec![b'h', b'e', b'l', b'l', b'o', b'\r', b'\n', 0];
         assert_eq!(
             std::str::from_utf8(&state.buffer),
@@ -95,9 +164,10 @@ mod tests {
     fn shift_single_unterminated_moved() {
         let mut state = ReadState {
             buffer: b"hello\r\nworld\0\0\0\0".to_vec(),
-            cursor: 7,
+            read_cursor: 7,
+            write_cursor: 0,
         };
-        state.shift_ramaining();
+        state.shift_remaining();
         let expected = b"world\0\0\0\0\0\0\0\0\0\0\0".to_vec();
         assert_eq!(
             std::str::from_utf8(&state.buffer),
@@ -108,9 +178,10 @@ mod tests {
     fn shift_single_terminated_moved() {
         let mut state = ReadState {
             buffer: b"hello\r\nworld\r\n\0\0\0\0\0\0\0\0".to_vec(),
-            cursor: 7,
+            read_cursor: 7,
+            write_cursor: 0,
         };
-        state.shift_ramaining();
+        state.shift_remaining();
         let expected = b"world\r\n\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0".to_vec();
         assert_eq!(
             std::str::from_utf8(&state.buffer),
@@ -122,7 +193,8 @@ mod tests {
     fn empty_next() {
         let mut state = ReadState {
             buffer: b"\0\0\0\0\0\0\0\0".to_vec(),
-            cursor: 0,
+            read_cursor: 0,
+            write_cursor: 0,
         };
         assert_eq!(state.next(), None);
     }
@@ -130,7 +202,8 @@ mod tests {
     fn depleted_next() {
         let mut state = ReadState {
             buffer: b"hello\0\0\0\0\0\0\0\0".to_vec(),
-            cursor: 5,
+            read_cursor: 5,
+            write_cursor: 0,
         };
         assert_eq!(state.next(), None);
     }
@@ -138,35 +211,38 @@ mod tests {
     fn one_world_next() {
         let mut state = ReadState {
             buffer: b"hello\r\n\0\0\0\0\0\0\0\0".to_vec(),
-            cursor: 0,
+            read_cursor: 0,
+            write_cursor: 0,
         };
         assert_eq!(state.next(), Some(b"hello\r\n".as_slice()));
-        assert_eq!(state.cursor, 7);
+        assert_eq!(state.read_cursor, 7);
     }
     #[test]
     fn tree_world_next() {
         let mut state = ReadState {
             buffer: b"hello\r\nworld\r\nnats\r\n\0\0\0\0\0\0\0\0".to_vec(),
-            cursor: 0,
+            read_cursor: 0,
+            write_cursor: 0,
         };
         assert_eq!(state.next(), Some(b"hello\r\n".as_slice()));
-        assert_eq!(state.cursor, 7);
+        assert_eq!(state.read_cursor, 7);
         assert_eq!(state.next(), Some(b"world\r\n".as_slice()));
-        assert_eq!(state.cursor, 14);
+        assert_eq!(state.read_cursor, 14);
         assert_eq!(state.next(), Some(b"nats\r\n".as_slice()));
-        assert_eq!(state.cursor, 20);
+        assert_eq!(state.read_cursor, 20);
         assert_eq!(state.next(), None);
-        assert_eq!(state.cursor, 20);
+        assert_eq!(state.read_cursor, 20);
     }
     #[test]
     fn partial_move_and_shift() {
         let mut state = ReadState {
             buffer: b"hello\r\nworld\r\nnats\r\n\0\0\0\0\0\0\0\0".to_vec(),
-            cursor: 0,
+            read_cursor: 0,
+            write_cursor: 0,
         };
         state.next();
         state.next();
-        state.shift_ramaining();
+        state.shift_remaining();
         let expected = b"nats\r\n\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0".to_vec();
         assert_eq!(
             std::str::from_utf8(&state.buffer),
@@ -177,12 +253,13 @@ mod tests {
     fn move_and_shift_non_terminated() {
         let mut state = ReadState {
             buffer: b"hello\r\nworld\r\nnats\0\0\0\0\0\0\0\0\0\0".to_vec(),
-            cursor: 0,
+            read_cursor: 0,
+            write_cursor: 0,
         };
         state.next();
         state.next();
         state.next();
-        state.shift_ramaining();
+        state.shift_remaining();
         let expected = b"nats\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0".to_vec();
         assert_eq!(
             std::str::from_utf8(&state.buffer),
@@ -193,13 +270,14 @@ mod tests {
     fn full_move_and_shift() {
         let mut state = ReadState {
             buffer: b"hello\r\nworld\r\nnats\r\n\0\0\0\0\0\0\0\0".to_vec(),
-            cursor: 0,
+            read_cursor: 0,
+            write_cursor: 0,
         };
         state.next();
         state.next();
         state.next();
-        assert_eq!(state.cursor, 20);
-        state.shift_ramaining();
+        assert_eq!(state.read_cursor, 20);
+        state.shift_remaining();
         let expected = b"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0".to_vec();
         assert_eq!(
             std::str::from_utf8(&state.buffer),
@@ -207,3 +285,38 @@ mod tests {
         );
     }
 }
+
+#[cfg(test)]
+mod write_buffer {
+    use super::*;
+
+    #[test]
+    fn write_2_msg() {
+        let mut state = ReadState::new(6);
+        assert_eq!(state.write(b"ab"), Ok(2));
+        assert_eq!(state.write(b"cd"), Ok(4));
+        assert_eq!(state.buffer.as_slice(), b"abcd\0\0");
+    }
+
+    #[test]
+    fn write_too_much() {
+        let mut state = ReadState::new(6);
+        assert_eq!(state.write(b"ab"), Ok(2));
+        assert_eq!(state.write(b"cd"), Ok(4));
+        assert_eq!(state.write(b"efg"), Err(CmdErr::BufferFull));
+    }
+    #[test]
+    fn write_after_shift() {
+        let mut state = ReadState::new(6);
+        assert_eq!(state.write(b"a\r\n"), Ok(3));
+        assert_eq!(state.write(b"c\r\n"), Ok(6));
+        while let Some(s) = state.next() {
+            eprintln!("next {s:?}");
+        }
+        state.shift_remaining();
+        assert_eq!(state.buffer.as_slice(), b"\0\0\0\0\0\0");
+        let res = state.write(b"efg");
+        assert_eq!(state.buffer.as_slice(), b"efg\0\0\0");
+        assert_eq!(res, Ok(3));
+    }
+}
diff --git a/src/error.rs b/src/error.rs
index bd91378..318aa4d 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -14,4 +14,6 @@ pub enum CmdErr {
     ExpectLen,
     #[error("Unable to write to client")]
     WriteFailed,
+    #[error("Server is overloaded and can't handle message")]
+    BufferFull,
 }