diff --git a/Cargo.toml b/Cargo.toml
index abb5e83..ceec139 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,12 @@ license = "MIT"
 keywords = ["kcp", "bindings"]
 
 [dependencies]
+bytes = "1"
+tokio = { version = "1", features = ["full"] }
+dashmap = "6.1.0"
+zerocopy = { version = "0.7", features = ["derive", "simd"] }
+bitflags = "2.5"
+parking_lot = "0.12.3"
 
 [build-dependencies]
 bindgen = "0.71.1"
diff --git a/src/endpoint.rs b/src/endpoint.rs
new file mode 100644
index 0000000..7a50fdb
--- /dev/null
+++ b/src/endpoint.rs
@@ -0,0 +1,325 @@
+use std::sync::{
+    atomic::{AtomicBool, AtomicU32},
+    Arc,
+};
+
+use bytes::BytesMut;
+use dashmap::DashMap;
+use parking_lot::Mutex;
+use tokio::{select, sync::Notify, task::JoinSet};
+
+use crate::{
+    error::Error,
+    ffi_safe::{Kcp, KcpConfig},
+    packet_def::KcpPacket,
+};
+
+pub type Sender<T> = tokio::sync::mpsc::Sender<T>;
+pub type Receiver<T> = tokio::sync::mpsc::Receiver<T>;
+
+pub type KcpPakcetSender = Sender<KcpPacket>;
+pub type KcpPacketReceiver = Receiver<KcpPacket>;
+
+pub type KcpStreamSender = Sender<BytesMut>;
+pub type KcpStreamReceiver = Receiver<BytesMut>;
+
+enum KcpClientState {
+    SynSent,
+    Established,
+    Fin,
+}
+
+enum KcpServerState {
+    SynReceived,
+    Established,
+    Fin,
+}
+
+enum KcpConnectionState {
+    Client(KcpClientState),
+    Server(KcpServerState),
+}
+
+struct KcpConnectionInner {
+    conv: u32,
+
+    update_notifier: Notify,
+    recv_notifier: Notify,
+    send_notifier: Notify,
+
+    has_new_input: AtomicBool,
+    waiting_new_send_window: AtomicBool,
+}
+
+struct KcpConnection {
+    conv: u32,
+    kcp: Arc<Mutex<Box<Kcp>>>,
+
+    inner: Arc<KcpConnectionInner>,
+
+    send_sender: Sender<BytesMut>,
+    send_receiver: Option<Receiver<BytesMut>>,
+
+    recv_sender: Sender<BytesMut>,
+    recv_receiver: Option<Receiver<BytesMut>>,
+
+    tasks: JoinSet<()>,
+}
+
+impl KcpConnection {
+    fn new(conv: u32) -> Result<Self, Error> {
+        let kcp = Kcp::new(KcpConfig::new(conv))?;
+
+        let (send_sender, send_receiver) = tokio::sync::mpsc::channel(16);
+        let (recv_sender, recv_receiver) = tokio::sync::mpsc::channel(16);
+
+        Ok(Self {
+            conv,
+            kcp: Arc::new(Mutex::new(kcp)),
+
+            inner: Arc::new(KcpConnectionInner {
+                conv,
+
+                update_notifier: Notify::new(),
+                recv_notifier: Notify::new(),
+                send_notifier: Notify::new(),
+
+                has_new_input: AtomicBool::new(false),
+                waiting_new_send_window: AtomicBool::new(false),
+            }),
+
+            send_sender,
+            send_receiver: Some(send_receiver),
+
+            recv_sender,
+            recv_receiver: Some(recv_receiver),
+
+            tasks: JoinSet::new(),
+        })
+    }
+
+    fn run(&mut self, output_sender: KcpPakcetSender) {
+        self.kcp
+            .lock()
+            .set_output_cb(Box::new(move |conv, data: BytesMut| {
+                let mut kcp_packet = KcpPacket::new_with_payload(&data);
+                kcp_packet
+                    .mut_header()
+                    .set_conv(conv)
+                    .set_len(data.len() as u16)
+                    .set_data(true);
+                println!("conv {} send output data: {:?}", conv, kcp_packet);
+                let _ = output_sender.try_send(kcp_packet);
+                Ok(())
+            }));
+
+        // kcp updater
+        let inner = self.inner.clone();
+        let kcp = self.kcp.clone();
+        self.tasks.spawn(async move {
+            loop {
+                let next_update_ms = kcp.lock().next_update_delay_ms();
+                select! {
+                    _ = tokio::time::sleep(tokio::time::Duration::from_millis(next_update_ms as u64)) => {}
+                    _ = inner.update_notifier.notified() => {}
+                }
+
+                kcp.lock().update();
+
+                if inner.has_new_input.swap(false, std::sync::atomic::Ordering::SeqCst) {
+                    inner.recv_notifier.notify_one();
+                }
+
+                if inner.waiting_new_send_window.swap(false, std::sync::atomic::Ordering::SeqCst) {
+                    inner.send_notifier.notify_one();
+                }
+            }
+        });
+
+        // handle packet send
+        let kcp = self.kcp.clone();
+        let inner = self.inner.clone();
+        let mut send_receiver = self.send_receiver.take().unwrap();
+        self.tasks.spawn(async move {
+            while let Some(data) = send_receiver.recv().await {
+                loop {
+                    let (waitsnd, sndwnd) = {
+                        let kcp = kcp.lock();
+                        (kcp.waitsnd(), kcp.sendwnd())
+                    };
+                    if waitsnd > 2 * sndwnd {
+                        inner
+                            .waiting_new_send_window
+                            .store(true, std::sync::atomic::Ordering::SeqCst);
+                        inner.send_notifier.notified().await;
+                    } else {
+                        break;
+                    }
+                }
+                kcp.lock().send(data.freeze()).unwrap();
+            }
+        });
+
+        // handle packet recv
+        let kcp = self.kcp.clone();
+        let inner = self.inner.clone();
+        let recv_sender = self.recv_sender.clone();
+        self.tasks.spawn(async move {
+            let mut buf = BytesMut::new();
+            loop {
+                if buf.capacity() < 1024 {
+                    buf.reserve(4096);
+                }
+                let ret = kcp.lock().recv(&mut buf);
+                if let Err(_) = ret {
+                    println!("recv error, conv: {}", inner.conv);
+                    inner.recv_notifier.notified().await;
+                } else {
+                    println!("recv data: {:?}", buf);
+                    assert_ne!(0, buf.len());
+                    let send_ret = recv_sender.send(buf.split()).await;
+                    if let Err(_) = send_ret {
+                        break;
+                    }
+                }
+            }
+        });
+    }
+
+    fn handle_input(&mut self, packet: KcpPacket) {
+        let _ = self.kcp.lock().handle_input(packet.payload());
+        self.inner
+            .has_new_input
+            .store(true, std::sync::atomic::Ordering::SeqCst);
+        self.inner.update_notifier.notify_one();
+    }
+
+    fn send_sender(&self) -> KcpStreamSender {
+        self.send_sender.clone()
+    }
+
+    fn recv_receiver(&mut self) -> KcpStreamReceiver {
+        self.recv_receiver.take().unwrap()
+    }
+}
+
+pub struct KcpEndpoint {
+    cur_conv: AtomicU32,
+    established_map: Arc<DashMap<u32, KcpConnection>>,
+
+    input_sender: KcpPakcetSender,
+    input_receiver: Option<KcpPacketReceiver>,
+
+    output_sender: KcpPakcetSender,
+    output_receiver: Option<KcpPacketReceiver>,
+
+    tasks: JoinSet<()>,
+}
+
+impl KcpEndpoint {
+    pub fn new() -> Self {
+        let (input_sender, input_receiver) = tokio::sync::mpsc::channel(1024);
+        let (output_sender, output_receiver) = tokio::sync::mpsc::channel(1024);
+
+        Self {
+            cur_conv: AtomicU32::new(0),
+            established_map: Arc::new(DashMap::new()),
+
+            input_sender,
+            input_receiver: Some(input_receiver),
+
+            output_sender,
+            output_receiver: Some(output_receiver),
+
+            tasks: JoinSet::new(),
+        }
+    }
+
+    pub async fn run(&mut self) {
+        let mut input_receiver = self.input_receiver.take().unwrap();
+        let established_map = self.established_map.clone();
+
+        self.tasks.spawn(async move {
+            while let Some(packet) = input_receiver.recv().await {
+                let conv = packet.header().conv();
+                if packet.header().is_data() {
+                    let Some(mut conn) = established_map.get_mut(&conv) else {
+                        continue;
+                    };
+                    let _ = conn.handle_input(packet);
+                }
+            }
+        });
+    }
+
+    pub fn add_established(&mut self, conv: u32) -> Result<(), Error> {
+        let mut conn = KcpConnection::new(conv)?;
+        conn.run(self.output_sender.clone());
+
+        self.established_map.insert(conv, conn);
+
+        Ok(())
+    }
+
+    pub fn output_receiver(&mut self) -> Option<KcpPacketReceiver> {
+        self.output_receiver.take()
+    }
+
+    pub fn input_sender(&self) -> KcpPakcetSender {
+        self.input_sender.clone()
+    }
+
+    pub fn conn_sender_receiver(&self, conv: u32) -> Option<(KcpStreamSender, KcpStreamReceiver)> {
+        let mut conn = self.established_map.get_mut(&conv)?;
+        Some((conn.send_sender(), conn.recv_receiver()))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn test_kcp_endpoint() {
+        let mut client_endpoint = KcpEndpoint::new();
+        let mut server_endpoint = KcpEndpoint::new();
+
+        client_endpoint.run().await;
+        server_endpoint.run().await;
+
+        let _ = client_endpoint.add_established(1).unwrap();
+        let _ = server_endpoint.add_established(1).unwrap();
+
+        let client_input_sender = client_endpoint.input_sender();
+        let mut server_output_receiver = server_endpoint.output_receiver().unwrap();
+        let t1 = tokio::spawn(async move {
+            while let Some(packet) = server_output_receiver.recv().await {
+                let _ = client_input_sender.send(packet).await;
+            }
+        });
+
+        let server_input_sender = server_endpoint.input_sender();
+        let mut client_output_receiver = client_endpoint.output_receiver().unwrap();
+        let t2 = tokio::spawn(async move {
+            while let Some(packet) = client_output_receiver.recv().await {
+                let _ = server_input_sender.send(packet).await;
+            }
+        });
+
+        let (client_sender, mut client_receiver) = client_endpoint.conn_sender_receiver(1).unwrap();
+        let (server_sender, mut server_receiver) = server_endpoint.conn_sender_receiver(1).unwrap();
+
+        client_sender.send(BytesMut::from("hello")).await.unwrap();
+        let data = server_receiver.recv().await.unwrap();
+        assert_eq!("hello", String::from_utf8_lossy(&data));
+
+        server_sender.send(BytesMut::from("world")).await.unwrap();
+        let data = client_receiver.recv().await.unwrap();
+        assert_eq!("world", String::from_utf8_lossy(&data));
+
+        drop(client_endpoint);
+        drop(server_endpoint);
+
+        let _ = tokio::join!(t1, t2);
+    }
+}
diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..bb8a9a1
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,5 @@
+#[derive(Debug)]
+pub enum Error {
+    CreateConnectionFailed,
+    Unknown,
+}
diff --git a/src/ffi.rs b/src/ffi.rs
new file mode 100644
index 0000000..a38a13a
--- /dev/null
+++ b/src/ffi.rs
@@ -0,0 +1,5 @@
+#![allow(non_upper_case_globals)]
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+
+include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
diff --git a/src/ffi_safe.rs b/src/ffi_safe.rs
new file mode 100644
index 0000000..14c5308
--- /dev/null
+++ b/src/ffi_safe.rs
@@ -0,0 +1,192 @@
+use crate::{error::Error, ffi::*};
+use std::time::Instant;
+
+use bytes::{Bytes, BytesMut};
+
+#[derive(Debug, Clone, Copy)]
+pub struct KcpConfig {
+    pub conv: IUINT32,
+    pub mtu: Option<i32>,
+
+    pub sndwnd: Option<i32>,
+    pub rcvwnd: Option<i32>,
+
+    pub nodelay: Option<i32>,
+    pub interval: Option<i32>,
+    pub resend: Option<i32>,
+    pub nc: Option<i32>,
+}
+
+impl KcpConfig {
+    pub fn new(conv: IUINT32) -> Self {
+        Self {
+            conv,
+            mtu: None,
+            sndwnd: None,
+            rcvwnd: None,
+            nodelay: None,
+            interval: None,
+            resend: None,
+            nc: None,
+        }
+    }
+}
+
+pub type OutputCb = Box<dyn Fn(u32, BytesMut) -> Result<(), Error>>;
+
+pub struct Kcp {
+    kcp: *mut ikcpcb,
+    config: KcpConfig,
+    now: Instant,
+    output_cb: Option<Box<dyn Fn(u32, BytesMut) -> Result<(), Error>>>,
+
+    _marker: core::marker::PhantomData<(*mut u8, core::marker::PhantomPinned)>,
+}
+
+unsafe impl Send for Kcp {}
+
+unsafe extern "C" fn ikcp_output(
+    buf: *const ::std::os::raw::c_char,
+    len: ::std::os::raw::c_int,
+    kcp: *mut ikcpcb,
+    this: *mut ::std::os::raw::c_void,
+) -> i32 {
+    // convert this to KcpConnection
+    let kcp_connection = &mut *(this as *mut Kcp);
+    assert_eq!(kcp_connection.kcp, kcp);
+
+    let buf = BytesMut::from(std::slice::from_raw_parts(buf as *const u8, len as usize));
+
+    // TODO: handle output error
+    let _ = kcp_connection.handle_output_callback(buf);
+
+    // kcp doesn't care about the return value
+    0
+}
+
+impl Kcp {
+    pub fn new(config: KcpConfig) -> Result<Box<Self>, Error> {
+        unsafe {
+            let conv = config.conv;
+            let mut ret = Box::new(Self {
+                kcp: std::ptr::null_mut(),
+                config,
+                now: Instant::now(),
+                output_cb: None,
+                _marker: core::marker::PhantomData,
+            });
+
+            let kcp = ikcp_create(conv, &mut *ret as *mut Kcp as *mut ::std::os::raw::c_void);
+            if kcp.is_null() {
+                return Err(Error::CreateConnectionFailed);
+            }
+
+            ret.kcp = kcp;
+
+            ikcp_setoutput(kcp, Some(ikcp_output));
+
+            ret.apply_config()?;
+
+            return Ok(ret);
+        }
+    }
+
+    pub fn set_output_cb(&mut self, output_cb: OutputCb) {
+        self.output_cb = Some(output_cb);
+    }
+
+    pub fn handle_input(&mut self, data: &[u8]) -> Result<(), Error> {
+        let ret = unsafe { ikcp_input(self.kcp, data.as_ptr() as *const i8, data.len() as i64) };
+        if ret < 0 {
+            return Err(Error::Unknown);
+        } else {
+            return Ok(());
+        }
+    }
+
+    pub fn update(&mut self) {
+        unsafe {
+            ikcp_update(self.kcp, self.now.elapsed().as_millis() as IUINT32);
+        }
+    }
+
+    pub fn next_update_delay_ms(&mut self) -> IUINT32 {
+        let current = self.now.elapsed().as_millis() as IUINT32;
+        let next = unsafe { ikcp_check(self.kcp, current) };
+        next - current
+    }
+
+    pub fn send(&mut self, data: Bytes) -> Result<usize, Error> {
+        let ret = unsafe { ikcp_send(self.kcp, data.as_ptr() as *const i8, data.len() as i32) };
+        if ret < 0 {
+            return Err(Error::Unknown);
+        } else {
+            return Ok(ret as usize);
+        }
+    }
+
+    pub fn recv(&mut self, buf: &mut BytesMut) -> Result<(), Error> {
+        let ret =
+            unsafe { ikcp_recv(self.kcp, buf.as_mut_ptr() as *mut i8, buf.capacity() as i32) };
+        if ret < 0 {
+            return Err(Error::Unknown);
+        } else {
+            unsafe {
+                buf.set_len(ret as usize);
+            }
+            return Ok(());
+        }
+    }
+
+    pub fn waitsnd(&self) -> i32 {
+        unsafe { ikcp_waitsnd(self.kcp) }
+    }
+
+    pub fn sendwnd(&self) -> i32 {
+        // see IKCP_WND_SND
+        self.config.sndwnd.unwrap_or(32)
+    }
+
+    fn handle_output_callback(&self, buf: BytesMut) -> Result<(), Error> {
+        (self.output_cb.as_ref().unwrap())(self.config.conv, buf)
+    }
+
+    fn apply_config(&mut self) -> Result<(), Error> {
+        unsafe {
+            let ret = ikcp_setmtu(self.kcp, self.config.mtu.unwrap_or(1200));
+            if ret < 0 {
+                return Err(Error::Unknown);
+            }
+
+            let ret = ikcp_wndsize(
+                self.kcp,
+                self.config.sndwnd.unwrap_or(-1),
+                self.config.rcvwnd.unwrap_or(-1),
+            );
+            if ret < 0 {
+                return Err(Error::Unknown);
+            }
+
+            let ret = ikcp_nodelay(
+                self.kcp,
+                self.config.nodelay.unwrap_or(-1),
+                self.config.interval.unwrap_or(-1),
+                self.config.resend.unwrap_or(-1),
+                self.config.nc.unwrap_or(-1),
+            );
+            if ret < 0 {
+                return Err(Error::Unknown);
+            }
+        }
+
+        return Ok(());
+    }
+}
+
+impl Drop for Kcp {
+    fn drop(&mut self) {
+        unsafe {
+            ikcp_release(self.kcp);
+        }
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index a38a13a..c6d3f71 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,5 +1,6 @@
-#![allow(non_upper_case_globals)]
-#![allow(non_camel_case_types)]
-#![allow(non_snake_case)]
+mod ffi;
+mod packet_def;
 
-include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
+pub mod error;
+pub mod endpoint;
+pub mod ffi_safe;
diff --git a/src/packet_def.rs b/src/packet_def.rs
new file mode 100644
index 0000000..e92ef9b
--- /dev/null
+++ b/src/packet_def.rs
@@ -0,0 +1,161 @@
+use bytes::{Bytes, BytesMut};
+use zerocopy::{AsBytes, FromBytes, FromZeroes};
+
+bitflags::bitflags! {
+    struct KcpPacketHeaderFlags: u8 {
+        const SYN = 0b0000_0001;
+        const ACK = 0b0000_0010;
+        const FIN = 0b0000_0100;
+        const DATA = 0b0000_1000;
+
+        const _ = !0;
+    }
+}
+
+#[repr(C, packed)]
+#[derive(AsBytes, FromBytes, FromZeroes, Clone, Debug, Default)]
+pub struct KcpPacketHeader {
+    conv: u32,
+    len: u16,
+    flag: u8,
+    rsv: u8,
+}
+
+impl KcpPacketHeader {
+    pub fn conv(&self) -> u32 {
+        self.conv
+    }
+
+    pub fn len(&self) -> u16 {
+        self.len
+    }
+
+    pub fn is_syn(&self) -> bool {
+        KcpPacketHeaderFlags::from_bits(self.flag)
+            .unwrap()
+            .contains(KcpPacketHeaderFlags::SYN)
+    }
+
+    pub fn is_ack(&self) -> bool {
+        KcpPacketHeaderFlags::from_bits(self.flag)
+            .unwrap()
+            .contains(KcpPacketHeaderFlags::ACK)
+    }
+
+    pub fn is_fin(&self) -> bool {
+        KcpPacketHeaderFlags::from_bits(self.flag)
+            .unwrap()
+            .contains(KcpPacketHeaderFlags::FIN)
+    }
+
+    pub fn is_data(&self) -> bool {
+        KcpPacketHeaderFlags::from_bits(self.flag)
+            .unwrap()
+            .contains(KcpPacketHeaderFlags::DATA)
+    }
+
+    pub fn set_conv(&mut self, conv: u32) -> &mut Self {
+        self.conv = conv;
+        self
+    }
+
+    pub fn set_len(&mut self, len: u16) -> &mut Self {
+        self.len = len;
+        self
+    }
+
+    pub fn set_syn(&mut self, syn: bool) -> &mut Self {
+        let mut flags = KcpPacketHeaderFlags::from_bits(self.flag).unwrap();
+        if syn {
+            flags.insert(KcpPacketHeaderFlags::SYN);
+        } else {
+            flags.remove(KcpPacketHeaderFlags::SYN);
+        }
+        self.flag = flags.bits();
+        self
+    }
+
+    pub fn set_ack(&mut self, ack: bool) -> &mut Self {
+        let mut flags = KcpPacketHeaderFlags::from_bits(self.flag).unwrap();
+        if ack {
+            flags.insert(KcpPacketHeaderFlags::ACK);
+        } else {
+            flags.remove(KcpPacketHeaderFlags::ACK);
+        }
+        self.flag = flags.bits();
+        self
+    }
+
+    pub fn set_fin(&mut self, fin: bool) -> &mut Self {
+        let mut flags = KcpPacketHeaderFlags::from_bits(self.flag).unwrap();
+        if fin {
+            flags.insert(KcpPacketHeaderFlags::FIN);
+        } else {
+            flags.remove(KcpPacketHeaderFlags::FIN);
+        }
+        self.flag = flags.bits();
+        self
+    }
+
+    pub fn set_data(&mut self, data: bool) -> &mut Self {
+        let mut flags = KcpPacketHeaderFlags::from_bits(self.flag).unwrap();
+        if data {
+            flags.insert(KcpPacketHeaderFlags::DATA);
+        } else {
+            flags.remove(KcpPacketHeaderFlags::DATA);
+        }
+        self.flag = flags.bits();
+        self
+    }
+}
+
+#[derive(Debug)]
+pub struct KcpPacket {
+    inner: BytesMut,
+}
+
+impl From<BytesMut> for KcpPacket {
+    fn from(inner: BytesMut) -> Self {
+        Self { inner }
+    }
+}
+
+impl Into<BytesMut> for KcpPacket {
+    fn into(self) -> BytesMut {
+        self.inner
+    }
+}
+
+impl Into<Bytes> for KcpPacket {
+    fn into(self) -> Bytes {
+        self.inner.freeze()
+    }
+}
+
+impl KcpPacket {
+    pub fn new(cap: Option<usize>) -> Self {
+        Self {
+            inner: BytesMut::with_capacity(cap.unwrap_or(std::mem::size_of::<KcpPacketHeader>())),
+        }
+    }
+
+    pub fn new_with_payload(payload: &[u8]) -> Self {
+        let mut inner =
+            BytesMut::with_capacity(std::mem::size_of::<KcpPacketHeader>() + payload.len());
+        inner.resize(std::mem::size_of::<KcpPacketHeader>(), 0);
+        inner.extend_from_slice(payload);
+        Self { inner }
+    }
+
+    pub fn mut_header(&mut self) -> &mut KcpPacketHeader {
+        KcpPacketHeader::mut_from_prefix(&mut self.inner).unwrap()
+    }
+
+    pub fn header(&self) -> &KcpPacketHeader {
+        KcpPacketHeader::ref_from_prefix(&self.inner).unwrap()
+    }
+
+    pub fn payload(&self) -> &[u8] {
+        &self.inner[std::mem::size_of::<KcpPacketHeader>()..]
+    }
+}