diff --git a/transport/internet/kcp/connection.go b/transport/internet/kcp/connection.go
new file mode 100644
index 00000000..6de1b687
--- /dev/null
+++ b/transport/internet/kcp/connection.go
@@ -0,0 +1,406 @@
+package kcp
+
+import (
+	"errors"
+	"io"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/v2ray/v2ray-core/common/alloc"
+	"github.com/v2ray/v2ray-core/common/log"
+)
+
+var (
+	errTimeout        = errors.New("i/o timeout")
+	errBrokenPipe     = errors.New("broken pipe")
+	errClosedListener = errors.New("Listener closed.")
+)
+
+const (
+	basePort       = 20000 // minimum port for listening
+	maxPort        = 65535 // maximum port for listening
+	defaultWndSize = 128   // default window size, in packet
+	mtuLimit       = 4096
+	rxQueueLimit   = 8192
+	rxFecLimit     = 2048
+
+	headerSize        = 2
+	cmdData    uint16 = 0
+	cmdClose   uint16 = 1
+)
+
+type Command byte
+
+var (
+	CommandData      Command = 0
+	CommandTerminate Command = 1
+)
+
+type Option byte
+
+var (
+	OptionClose Option = 1
+)
+
+type ConnState byte
+
+var (
+	ConnStateActive       ConnState = 0
+	ConnStateReadyToClose ConnState = 1
+	ConnStatePeerClosed   ConnState = 2
+	ConnStateClosed       ConnState = 4
+)
+
+func nowMillisec() int64 {
+	now := time.Now()
+	return now.Unix()*1000 + int64(now.Nanosecond()/1000000)
+}
+
+// UDPSession defines a KCP session implemented by UDP
+type UDPSession struct {
+	sync.Mutex
+	state         ConnState
+	kcp           *KCP // the core ARQ
+	kcpAccess     sync.Mutex
+	block         Authenticator
+	needUpdate    bool
+	local, remote net.Addr
+	rd            time.Time // read deadline
+	wd            time.Time // write deadline
+	chReadEvent   chan struct{}
+	chWriteEvent  chan struct{}
+	ackNoDelay    bool
+	writer        io.WriteCloser
+	since         int64
+}
+
+// newUDPSession create a new udp session for client or server
+func newUDPSession(conv uint32, writerCloser io.WriteCloser, local *net.UDPAddr, remote *net.UDPAddr, block Authenticator) *UDPSession {
+	sess := new(UDPSession)
+	sess.local = local
+	sess.chReadEvent = make(chan struct{}, 1)
+	sess.chWriteEvent = make(chan struct{}, 1)
+	sess.remote = remote
+	sess.block = block
+	sess.writer = writerCloser
+	sess.since = nowMillisec()
+
+	mtu := uint32(effectiveConfig.Mtu - block.HeaderSize() - headerSize)
+	sess.kcp = NewKCP(conv, mtu, func(buf []byte, size int) {
+		log.Info(sess.local, " kcp output: ", buf[:size])
+		if size >= IKCP_OVERHEAD {
+			ext := alloc.NewBuffer().Clear().Append(buf[:size])
+			cmd := cmdData
+			opt := Option(0)
+			if sess.state == ConnStateReadyToClose {
+				opt = OptionClose
+			}
+			ext.Prepend([]byte{byte(cmd), byte(opt)})
+			sess.output(ext)
+		}
+	})
+	sess.kcp.WndSize(effectiveConfig.Sndwnd, effectiveConfig.Rcvwnd)
+	sess.kcp.NoDelay(1, 20, 2, 1)
+	sess.ackNoDelay = effectiveConfig.Acknodelay
+	sess.kcp.current = sess.Elapsed()
+
+	go sess.updateTask()
+
+	log.Info("Created KCP conn to ", sess.RemoteAddr())
+	return sess
+}
+
+func (this *UDPSession) Elapsed() uint32 {
+	return uint32(nowMillisec() - this.since)
+}
+
+// Read implements the Conn Read method.
+func (s *UDPSession) Read(b []byte) (int, error) {
+	if s.state == ConnStateReadyToClose || s.state == ConnStateClosed {
+		return 0, io.EOF
+	}
+
+	for {
+		s.Lock()
+		if s.state == ConnStateReadyToClose || s.state == ConnStateClosed {
+			s.Unlock()
+			return 0, io.EOF
+		}
+
+		if !s.rd.IsZero() {
+			if time.Now().After(s.rd) {
+				s.Unlock()
+				return 0, errTimeout
+			}
+		}
+
+		nBytes := s.kcp.Recv(b)
+		if nBytes > 0 {
+			s.Unlock()
+			return nBytes, nil
+		}
+
+		var timeout <-chan time.Time
+		if !s.rd.IsZero() {
+			delay := s.rd.Sub(time.Now())
+			timeout = time.After(delay)
+		}
+
+		s.Unlock()
+		select {
+		case <-s.chReadEvent:
+		case <-timeout:
+			return 0, errTimeout
+		}
+	}
+}
+
+// Write implements the Conn Write method.
+func (s *UDPSession) Write(b []byte) (int, error) {
+	log.Info("Trying to write ", len(b), " bytes. ", s.local)
+	if s.state == ConnStateReadyToClose ||
+		s.state == ConnStatePeerClosed ||
+		s.state == ConnStateClosed {
+		return 0, io.ErrClosedPipe
+	}
+
+	for {
+		s.Lock()
+		if s.state == ConnStateReadyToClose ||
+			s.state == ConnStatePeerClosed ||
+			s.state == ConnStateClosed {
+			s.Unlock()
+			return 0, io.ErrClosedPipe
+		}
+
+		if !s.wd.IsZero() {
+			if time.Now().After(s.wd) { // timeout
+				s.Unlock()
+				return 0, errTimeout
+			}
+		}
+
+		if s.kcp.WaitSnd() < int(s.kcp.snd_wnd) {
+			nBytes := len(b)
+			log.Info("Writing ", nBytes, " bytes.", s.local)
+			s.kcp.Send(b)
+			s.kcp.current = s.Elapsed()
+			s.kcp.flush()
+			s.Unlock()
+			return nBytes, nil
+		}
+
+		var timeout <-chan time.Time
+		if !s.wd.IsZero() {
+			delay := s.wd.Sub(time.Now())
+			timeout = time.After(delay)
+		}
+		s.Unlock()
+
+		// wait for write event or timeout
+		select {
+		case <-s.chWriteEvent:
+		case <-timeout:
+			return 0, errTimeout
+		}
+	}
+}
+
+func (this *UDPSession) Terminate() {
+	if this.state == ConnStateClosed {
+		return
+	}
+	this.Lock()
+	defer this.Unlock()
+
+	this.state = ConnStateClosed
+	this.writer.Close()
+}
+
+func (this *UDPSession) NotifyTermination() {
+	for i := 0; i < 16; i++ {
+		this.Lock()
+		if this.state == ConnStateClosed {
+			this.Unlock()
+			return
+		}
+		buffer := alloc.NewSmallBuffer().Clear()
+		buffer.AppendBytes(byte(CommandTerminate), byte(OptionClose), byte(0), byte(0), byte(0), byte(0))
+		this.output(buffer)
+		time.Sleep(time.Second)
+		this.Unlock()
+	}
+	this.Terminate()
+}
+
+// Close closes the connection.
+func (s *UDPSession) Close() error {
+	log.Info("Closed ", s.local)
+	s.Lock()
+	defer s.Unlock()
+
+	if s.state == ConnStateActive {
+		s.state = ConnStateReadyToClose
+		if s.kcp.WaitSnd() == 0 {
+			go s.NotifyTermination()
+		}
+	}
+
+	if s.state == ConnStatePeerClosed {
+		go s.Terminate()
+	}
+
+	return nil
+}
+
+// LocalAddr returns the local network address. The Addr returned is shared by all invocations of LocalAddr, so do not modify it.
+func (s *UDPSession) LocalAddr() net.Addr {
+	return s.local
+}
+
+// RemoteAddr returns the remote network address. The Addr returned is shared by all invocations of RemoteAddr, so do not modify it.
+func (s *UDPSession) RemoteAddr() net.Addr { return s.remote }
+
+// SetDeadline sets the deadline associated with the listener. A zero time value disables the deadline.
+func (s *UDPSession) SetDeadline(t time.Time) error {
+	s.Lock()
+	defer s.Unlock()
+	s.rd = t
+	s.wd = t
+	return nil
+}
+
+// SetReadDeadline implements the Conn SetReadDeadline method.
+func (s *UDPSession) SetReadDeadline(t time.Time) error {
+	s.Lock()
+	defer s.Unlock()
+	s.rd = t
+	return nil
+}
+
+// SetWriteDeadline implements the Conn SetWriteDeadline method.
+func (s *UDPSession) SetWriteDeadline(t time.Time) error {
+	s.Lock()
+	defer s.Unlock()
+	s.wd = t
+	return nil
+}
+
+func (s *UDPSession) output(payload *alloc.Buffer) {
+	defer payload.Release()
+
+	if s.state == ConnStatePeerClosed || s.state == ConnStateClosed {
+		return
+	}
+	s.block.Seal(payload)
+
+	s.writer.Write(payload.Value)
+}
+
+// kcp update, input loop
+func (s *UDPSession) updateTask() {
+	ticker := time.NewTicker(20 * time.Millisecond)
+	defer ticker.Stop()
+
+	var nextupdate uint32 = 0
+	for range ticker.C {
+		s.Lock()
+		if s.state == ConnStateClosed {
+			s.Unlock()
+			return
+		}
+		current := s.Elapsed()
+		if !s.needUpdate && nextupdate == 0 {
+			nextupdate = s.kcp.Check(current)
+		}
+		current = s.Elapsed()
+		if s.needUpdate || current >= nextupdate {
+			log.Info("Updating KCP: ", current, " addr ", s.LocalAddr())
+			s.kcp.Update(current)
+			nextupdate = s.kcp.Check(current)
+			s.needUpdate = false
+		}
+		if s.kcp.WaitSnd() < int(s.kcp.snd_wnd) {
+			s.notifyWriteEvent()
+		}
+		s.Unlock()
+	}
+}
+
+func (s *UDPSession) notifyReadEvent() {
+	select {
+	case s.chReadEvent <- struct{}{}:
+	default:
+	}
+}
+
+func (s *UDPSession) notifyWriteEvent() {
+	select {
+	case s.chWriteEvent <- struct{}{}:
+	default:
+	}
+}
+
+func (this *UDPSession) MarkPeerClose() {
+	this.Lock()
+	defer this.Unlock()
+	if this.state == ConnStateReadyToClose {
+		this.state = ConnStateClosed
+		go this.Terminate()
+		return
+	}
+	if this.state == ConnStateActive {
+		this.state = ConnStatePeerClosed
+	}
+}
+
+func (s *UDPSession) kcpInput(data []byte) {
+	cmd := Command(data[0])
+	opt := Option(data[1])
+	if cmd == CommandTerminate {
+		go s.Terminate()
+		return
+	}
+	if opt == OptionClose {
+		go s.MarkPeerClose()
+	}
+	s.kcpAccess.Lock()
+	s.kcp.current = s.Elapsed()
+	log.Info(s.local, " kcp input: ", data[2:])
+	ret := s.kcp.Input(data[2:])
+	log.Info("kcp input returns ", ret)
+
+	if s.ackNoDelay {
+		s.kcp.current = s.Elapsed()
+		s.kcp.flush()
+	} else {
+		s.needUpdate = true
+	}
+	s.kcpAccess.Unlock()
+	s.notifyReadEvent()
+}
+
+func (this *UDPSession) FetchInputFrom(conn net.Conn) {
+	go func() {
+		for {
+			payload := alloc.NewBuffer()
+			nBytes, err := conn.Read(payload.Value)
+			if err != nil {
+				return
+			}
+			payload.Slice(0, nBytes)
+			if this.block.Open(payload) {
+				log.Info("Client fetching ", payload.Len(), " bytes.")
+				this.kcpInput(payload.Value)
+			}
+			payload.Release()
+		}
+	}()
+}
+
+func (this *UDPSession) Reusable() bool {
+	return false
+}
+
+func (this *UDPSession) SetReusable(b bool) {}
diff --git a/transport/internet/kcp/crypt.go b/transport/internet/kcp/crypt.go
index 02e963ab..7d769474 100644
--- a/transport/internet/kcp/crypt.go
+++ b/transport/internet/kcp/crypt.go
@@ -1,23 +1,64 @@
 package kcp
 
-type BlockCrypt interface {
+import (
+	"hash/fnv"
+
+	"github.com/v2ray/v2ray-core/common/alloc"
+	"github.com/v2ray/v2ray-core/common/serial"
+)
+
+type Authenticator interface {
+	HeaderSize() int
 	// Encrypt encrypts the whole block in src into dst.
 	// Dst and src may point at the same memory.
-	Encrypt(dst, src []byte)
+	Seal(buffer *alloc.Buffer)
 
 	// Decrypt decrypts the whole block in src into dst.
 	// Dst and src may point at the same memory.
-	Decrypt(dst, src []byte)
+	Open(buffer *alloc.Buffer) bool
+}
+
+type SimpleAuthenticator struct{}
+
+func NewSimpleAuthenticator() Authenticator {
+	return &SimpleAuthenticator{}
 }
 
-// None Encryption
-type NoneBlockCrypt struct {
-	xortbl []byte
+func (this *SimpleAuthenticator) HeaderSize() int {
+	return 6
 }
 
-func NewNoneBlockCrypt(key []byte) (BlockCrypt, error) {
-	return new(NoneBlockCrypt), nil
+func (this *SimpleAuthenticator) Seal(buffer *alloc.Buffer) {
+	var length uint16 = uint16(buffer.Len())
+	buffer.Prepend(serial.Uint16ToBytes(length))
+	fnvHash := fnv.New32a()
+	fnvHash.Write(buffer.Value)
+
+	buffer.SliceBack(4)
+	fnvHash.Sum(buffer.Value[:0])
+
+	for i := 4; i < buffer.Len(); i++ {
+		buffer.Value[i] ^= buffer.Value[i-4]
+	}
 }
 
-func (c *NoneBlockCrypt) Encrypt(dst, src []byte) {}
-func (c *NoneBlockCrypt) Decrypt(dst, src []byte) {}
+func (this *SimpleAuthenticator) Open(buffer *alloc.Buffer) bool {
+	for i := buffer.Len() - 1; i >= 4; i-- {
+		buffer.Value[i] ^= buffer.Value[i-4]
+	}
+
+	fnvHash := fnv.New32a()
+	fnvHash.Write(buffer.Value[4:])
+	if serial.BytesToUint32(buffer.Value[:4]) != fnvHash.Sum32() {
+		return false
+	}
+
+	length := serial.BytesToUint16(buffer.Value[4:6])
+	if buffer.Len()-6 != int(length) {
+		return false
+	}
+
+	buffer.SliceFrom(6)
+
+	return true
+}
diff --git a/transport/internet/kcp/crypt_test.go b/transport/internet/kcp/crypt_test.go
new file mode 100644
index 00000000..e57c28e4
--- /dev/null
+++ b/transport/internet/kcp/crypt_test.go
@@ -0,0 +1,22 @@
+package kcp_test
+
+import (
+	"testing"
+
+	"github.com/v2ray/v2ray-core/common/alloc"
+	"github.com/v2ray/v2ray-core/testing/assert"
+	. "github.com/v2ray/v2ray-core/transport/internet/kcp"
+)
+
+func TestSimpleAuthenticator(t *testing.T) {
+	assert := assert.On(t)
+
+	buffer := alloc.NewBuffer().Clear()
+	buffer.AppendBytes('a', 'b', 'c', 'd', 'e', 'f', 'g')
+
+	auth := NewSimpleAuthenticator()
+	auth.Seal(buffer)
+
+	assert.Bool(auth.Open(buffer)).IsTrue()
+	assert.String(buffer.String()).Equals("abcdefg")
+}
diff --git a/transport/internet/kcp/dialer.go b/transport/internet/kcp/dialer.go
index a66fd647..5b22b63e 100644
--- a/transport/internet/kcp/dialer.go
+++ b/transport/internet/kcp/dialer.go
@@ -5,6 +5,7 @@ import (
 	"math/rand"
 	"net"
 
+	"github.com/v2ray/v2ray-core/common/log"
 	v2net "github.com/v2ray/v2ray-core/common/net"
 	"github.com/v2ray/v2ray-core/transport/internet"
 )
@@ -14,37 +15,18 @@ var (
 )
 
 func DialKCP(src v2net.Address, dest v2net.Destination) (internet.Connection, error) {
-	var ip net.IP
-	if dest.Address().IsDomain() {
-		ips, err := net.LookupIP(dest.Address().Domain())
-		if err != nil {
-			return nil, err
-		}
-		if len(ips) == 0 {
-			return nil, ErrUnknownDestination
-		}
-		ip = ips[0]
-	} else {
-		ip = dest.Address().IP()
-	}
-	udpAddr := &net.UDPAddr{
-		IP:   ip,
-		Port: int(dest.Port()),
-	}
-
-	udpConn, err := net.ListenUDP("udp", &net.UDPAddr{})
+	log.Info("Dialling KCP to ", dest)
+	udpDest := v2net.UDPDestination(dest.Address(), dest.Port())
+	conn, err := internet.DialToDest(src, udpDest)
 	if err != nil {
 		return nil, err
 	}
 
-	cpip, _ := NewNoneBlockCrypt(nil)
-	session := newUDPSession(rand.Uint32(), nil, udpConn, udpAddr, cpip)
-	kcvn := &KCPVconn{hc: session}
-	err = kcvn.ApplyConf()
-	if err != nil {
-		return nil, err
-	}
-	return kcvn, nil
+	cpip := NewSimpleAuthenticator()
+	session := newUDPSession(rand.Uint32(), conn, conn.LocalAddr().(*net.UDPAddr), conn.RemoteAddr().(*net.UDPAddr), cpip)
+	session.FetchInputFrom(conn)
+
+	return session, nil
 }
 
 func init() {
diff --git a/transport/internet/kcp/kcp.go b/transport/internet/kcp/kcp.go
index b1f58086..42f6e66b 100644
--- a/transport/internet/kcp/kcp.go
+++ b/transport/internet/kcp/kcp.go
@@ -22,7 +22,7 @@ const (
 	IKCP_ASK_TELL    = 2  // need to send IKCP_CMD_WINS
 	IKCP_WND_SND     = 32
 	IKCP_WND_RCV     = 32
-	IKCP_MTU_DEF     = 1400
+	IKCP_MTU_DEF     = 1350
 	IKCP_ACK_FAST    = 3
 	IKCP_INTERVAL    = 100
 	IKCP_OVERHEAD    = 24
@@ -156,13 +156,13 @@ type KCP struct {
 
 // NewKCP create a new kcp control object, 'conv' must equal in two endpoint
 // from the same connection.
-func NewKCP(conv uint32, output Output) *KCP {
+func NewKCP(conv uint32, mtu uint32, output Output) *KCP {
 	kcp := new(KCP)
 	kcp.conv = conv
 	kcp.snd_wnd = IKCP_WND_SND
 	kcp.rcv_wnd = IKCP_WND_RCV
 	kcp.rmt_wnd = IKCP_WND_RCV
-	kcp.mtu = IKCP_MTU_DEF
+	kcp.mtu = mtu
 	kcp.mss = kcp.mtu - IKCP_OVERHEAD
 	kcp.buffer = make([]byte, (kcp.mtu+IKCP_OVERHEAD)*3)
 	kcp.rx_rto = IKCP_RTO_DEF
@@ -206,14 +206,14 @@ func (kcp *KCP) Recv(buffer []byte) (n int) {
 		return -1
 	}
 
-	peeksize := kcp.PeekSize()
-	if peeksize < 0 {
-		return -2
-	}
+	//peeksize := kcp.PeekSize()
+	//if peeksize < 0 {
+	//	return -2
+	//}
 
-	if peeksize > len(buffer) {
-		return -3
-	}
+	//if peeksize > len(buffer) {
+	//	return -3
+	//}
 
 	var fast_recover bool
 	if len(kcp.rcv_queue) >= int(kcp.rcv_wnd) {
@@ -224,13 +224,13 @@ func (kcp *KCP) Recv(buffer []byte) (n int) {
 	count := 0
 	for k := range kcp.rcv_queue {
 		seg := &kcp.rcv_queue[k]
+		if len(seg.data) > len(buffer) {
+			break
+		}
 		copy(buffer, seg.data)
 		buffer = buffer[len(seg.data):]
 		n += len(seg.data)
 		count++
-		if seg.frg == 0 {
-			break
-		}
 	}
 	kcp.rcv_queue = kcp.rcv_queue[count:]
 
@@ -901,3 +901,7 @@ func (kcp *KCP) WndSize(sndwnd, rcvwnd int) int {
 func (kcp *KCP) WaitSnd() int {
 	return len(kcp.snd_buf) + len(kcp.snd_queue)
 }
+
+func (kcp *KCP) WaitRcv() int {
+	return len(kcp.rcv_buf) + len(kcp.rcv_queue)
+}
diff --git a/transport/internet/kcp/listener.go b/transport/internet/kcp/listener.go
new file mode 100644
index 00000000..386727c8
--- /dev/null
+++ b/transport/internet/kcp/listener.go
@@ -0,0 +1,160 @@
+package kcp
+
+import (
+	"encoding/binary"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/v2ray/v2ray-core/common/alloc"
+	"github.com/v2ray/v2ray-core/common/log"
+	v2net "github.com/v2ray/v2ray-core/common/net"
+	"github.com/v2ray/v2ray-core/transport/internet"
+	"github.com/v2ray/v2ray-core/transport/internet/udp"
+)
+
+// Listener defines a server listening for connections
+type Listener struct {
+	sync.Mutex
+	running       bool
+	block         Authenticator
+	sessions      map[string]*UDPSession
+	awaitingConns chan *UDPSession
+	hub           *udp.UDPHub
+	localAddr     *net.UDPAddr
+}
+
+func NewListener(address v2net.Address, port v2net.Port) (*Listener, error) {
+	log.Info("Creating listener on ", address, ":", port)
+	l := &Listener{
+		block:         NewSimpleAuthenticator(),
+		sessions:      make(map[string]*UDPSession),
+		awaitingConns: make(chan *UDPSession, 64),
+		localAddr: &net.UDPAddr{
+			IP:   address.IP(),
+			Port: int(port),
+		},
+		running: true,
+	}
+	hub, err := udp.ListenUDP(address, port, l.OnReceive)
+	if err != nil {
+		return nil, err
+	}
+	l.hub = hub
+	log.Info("Listener created.")
+	return l, nil
+}
+
+func (this *Listener) OnReceive(payload *alloc.Buffer, src v2net.Destination) {
+	log.Info("Listener on receive from ", src)
+	defer payload.Release()
+
+	if valid := this.block.Open(payload); !valid {
+		log.Info("Listern discarding invalid payload.")
+		return
+	}
+	if !this.running {
+		return
+	}
+	this.Lock()
+	defer this.Unlock()
+	if !this.running {
+		return
+	}
+	srcAddrStr := src.NetAddr()
+	conn, found := this.sessions[srcAddrStr]
+	if !found {
+		conv := binary.LittleEndian.Uint32(payload.Value[2:6])
+		writer := &Writer{
+			hub:      this.hub,
+			dest:     src,
+			listener: this,
+		}
+		srcAddr := &net.UDPAddr{
+			IP:   src.Address().IP(),
+			Port: int(src.Port()),
+		}
+		log.Info("Listener creating new connection.")
+		conn = newUDPSession(conv, writer, this.localAddr, srcAddr, this.block)
+		select {
+		case this.awaitingConns <- conn:
+		case <-time.After(time.Second * 5):
+			conn.Close()
+			return
+		}
+		this.sessions[srcAddrStr] = conn
+	}
+	conn.kcpInput(payload.Value)
+}
+
+func (this *Listener) Remove(dest string) {
+	if !this.running {
+		return
+	}
+	this.Lock()
+	defer this.Unlock()
+	if !this.running {
+		return
+	}
+	delete(this.sessions, dest)
+}
+
+// Accept implements the Accept method in the Listener interface; it waits for the next call and returns a generic Conn.
+func (this *Listener) Accept() (internet.Connection, error) {
+	for {
+		if !this.running {
+			return nil, errClosedListener
+		}
+		select {
+		case conn := <-this.awaitingConns:
+			log.Info("Accepting connection from ", conn.RemoteAddr())
+			return conn, nil
+		case <-time.After(time.Second):
+
+		}
+	}
+}
+
+// Close stops listening on the UDP address. Already Accepted connections are not closed.
+func (this *Listener) Close() error {
+	if !this.running {
+		return errClosedListener
+	}
+	this.Lock()
+	defer this.Unlock()
+
+	this.running = false
+	close(this.awaitingConns)
+	this.hub.Close()
+
+	return nil
+}
+
+// Addr returns the listener's network address, The Addr returned is shared by all invocations of Addr, so do not modify it.
+func (this *Listener) Addr() net.Addr {
+	return this.localAddr
+}
+
+type Writer struct {
+	dest     v2net.Destination
+	hub      *udp.UDPHub
+	listener *Listener
+}
+
+func (this *Writer) Write(payload []byte) (int, error) {
+	log.Info("Writer writing to ", this.dest, " with ", len(payload), " bytes.")
+	return this.hub.WriteTo(payload, this.dest)
+}
+
+func (this *Writer) Close() error {
+	this.listener.Remove(this.dest.NetAddr())
+	return nil
+}
+
+func ListenKCP(address v2net.Address, port v2net.Port) (internet.Listener, error) {
+	return NewListener(address, port)
+}
+
+func init() {
+	internet.KCPListenFunc = ListenKCP
+}
diff --git a/transport/internet/kcp/sess.go b/transport/internet/kcp/sess.go
deleted file mode 100644
index 7a53e236..00000000
--- a/transport/internet/kcp/sess.go
+++ /dev/null
@@ -1,563 +0,0 @@
-package kcp
-
-import (
-	crand "crypto/rand"
-	"encoding/binary"
-	"errors"
-	"hash/crc32"
-	"io"
-	"log"
-	"math/rand"
-	"net"
-	"sync"
-	"time"
-
-	"golang.org/x/net/ipv4"
-)
-
-var (
-	errTimeout    = errors.New("i/o timeout")
-	errBrokenPipe = errors.New("broken pipe")
-)
-
-const (
-	basePort        = 20000 // minimum port for listening
-	maxPort         = 65535 // maximum port for listening
-	defaultWndSize  = 128   // default window size, in packet
-	otpSize         = 16    // magic number
-	crcSize         = 4     // 4bytes packet checksum
-	cryptHeaderSize = otpSize + crcSize
-	connTimeout     = 60 * time.Second
-	mtuLimit        = 4096
-	rxQueueLimit    = 8192
-	rxFecLimit      = 2048
-)
-
-type (
-	// UDPSession defines a KCP session implemented by UDP
-	UDPSession struct {
-		kcp           *KCP         // the core ARQ
-		conn          *net.UDPConn // the underlying UDP socket
-		block         BlockCrypt
-		needUpdate    bool
-		l             *Listener // point to server listener if it's a server socket
-		local, remote net.Addr
-		rd            time.Time // read deadline
-		wd            time.Time // write deadline
-		sockbuff      []byte    // kcp receiving is based on packet, I turn it into stream
-		die           chan struct{}
-		isClosed      bool
-		mu            sync.Mutex
-		chReadEvent   chan struct{}
-		chWriteEvent  chan struct{}
-		chTicker      chan time.Time
-		chUDPOutput   chan []byte
-		headerSize    int
-		lastInputTs   time.Time
-		ackNoDelay    bool
-	}
-)
-
-// newUDPSession create a new udp session for client or server
-func newUDPSession(conv uint32, l *Listener, conn *net.UDPConn, remote *net.UDPAddr, block BlockCrypt) *UDPSession {
-	sess := new(UDPSession)
-	sess.chTicker = make(chan time.Time, 1)
-	sess.chUDPOutput = make(chan []byte, rxQueueLimit)
-	sess.die = make(chan struct{})
-	sess.local = conn.LocalAddr()
-	sess.chReadEvent = make(chan struct{}, 1)
-	sess.chWriteEvent = make(chan struct{}, 1)
-	sess.remote = remote
-	sess.conn = conn
-	sess.l = l
-	sess.block = block
-	sess.lastInputTs = time.Now()
-
-	// caculate header size
-	if sess.block != nil {
-		sess.headerSize += cryptHeaderSize
-	}
-
-	sess.kcp = NewKCP(conv, func(buf []byte, size int) {
-		if size >= IKCP_OVERHEAD {
-			ext := make([]byte, sess.headerSize+size)
-			copy(ext[sess.headerSize:], buf)
-			sess.chUDPOutput <- ext
-		}
-	})
-	sess.kcp.WndSize(defaultWndSize, defaultWndSize)
-	sess.kcp.SetMtu(IKCP_MTU_DEF - sess.headerSize)
-
-	go sess.updateTask()
-	go sess.outputTask()
-	if l == nil { // it's a client connection
-		go sess.readLoop()
-	}
-
-	return sess
-}
-
-// Read implements the Conn Read method.
-func (s *UDPSession) Read(b []byte) (n int, err error) {
-	for {
-		s.mu.Lock()
-		if len(s.sockbuff) > 0 { // copy from buffer
-			n = copy(b, s.sockbuff)
-			s.sockbuff = s.sockbuff[n:]
-			s.mu.Unlock()
-			return n, nil
-		}
-
-		if s.isClosed {
-			s.mu.Unlock()
-			return 0, errBrokenPipe
-		}
-
-		if !s.rd.IsZero() {
-			if time.Now().After(s.rd) { // timeout
-				s.mu.Unlock()
-				return 0, errTimeout
-			}
-		}
-
-		if n := s.kcp.PeekSize(); n > 0 { // data arrived
-			if len(b) >= n {
-				s.kcp.Recv(b)
-			} else {
-				buf := make([]byte, n)
-				s.kcp.Recv(buf)
-				n = copy(b, buf)
-				s.sockbuff = buf[n:] // store remaining bytes into sockbuff for next read
-			}
-			s.mu.Unlock()
-			return n, nil
-		}
-
-		var timeout <-chan time.Time
-		if !s.rd.IsZero() {
-			delay := s.rd.Sub(time.Now())
-			timeout = time.After(delay)
-		}
-		s.mu.Unlock()
-
-		// wait for read event or timeout
-		select {
-		case <-s.chReadEvent:
-		case <-timeout:
-		case <-s.die:
-		}
-	}
-}
-
-// Write implements the Conn Write method.
-func (s *UDPSession) Write(b []byte) (n int, err error) {
-	for {
-		s.mu.Lock()
-		if s.isClosed {
-			s.mu.Unlock()
-			return 0, errBrokenPipe
-		}
-
-		if !s.wd.IsZero() {
-			if time.Now().After(s.wd) { // timeout
-				s.mu.Unlock()
-				return 0, errTimeout
-			}
-		}
-
-		if s.kcp.WaitSnd() < int(s.kcp.snd_wnd) {
-			n = len(b)
-			max := s.kcp.mss << 8
-			for {
-				if len(b) <= int(max) { // in most cases
-					s.kcp.Send(b)
-					break
-				} else {
-					s.kcp.Send(b[:max])
-					b = b[max:]
-				}
-			}
-			s.kcp.current = currentMs()
-			s.kcp.flush()
-			s.mu.Unlock()
-			return n, nil
-		}
-
-		var timeout <-chan time.Time
-		if !s.wd.IsZero() {
-			delay := s.wd.Sub(time.Now())
-			timeout = time.After(delay)
-		}
-		s.mu.Unlock()
-
-		// wait for write event or timeout
-		select {
-		case <-s.chWriteEvent:
-		case <-timeout:
-		case <-s.die:
-		}
-	}
-}
-
-// Close closes the connection.
-func (s *UDPSession) Close() error {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	if s.isClosed {
-		return errBrokenPipe
-	}
-	close(s.die)
-	s.isClosed = true
-	if s.l == nil { // client socket close
-		s.conn.Close()
-	}
-
-	return nil
-}
-
-// LocalAddr returns the local network address. The Addr returned is shared by all invocations of LocalAddr, so do not modify it.
-func (s *UDPSession) LocalAddr() net.Addr {
-	return s.local
-}
-
-// RemoteAddr returns the remote network address. The Addr returned is shared by all invocations of RemoteAddr, so do not modify it.
-func (s *UDPSession) RemoteAddr() net.Addr { return s.remote }
-
-// SetDeadline sets the deadline associated with the listener. A zero time value disables the deadline.
-func (s *UDPSession) SetDeadline(t time.Time) error {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	s.rd = t
-	s.wd = t
-	return nil
-}
-
-// SetReadDeadline implements the Conn SetReadDeadline method.
-func (s *UDPSession) SetReadDeadline(t time.Time) error {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	s.rd = t
-	return nil
-}
-
-// SetWriteDeadline implements the Conn SetWriteDeadline method.
-func (s *UDPSession) SetWriteDeadline(t time.Time) error {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	s.wd = t
-	return nil
-}
-
-// SetWindowSize set maximum window size
-func (s *UDPSession) SetWindowSize(sndwnd, rcvwnd int) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	s.kcp.WndSize(sndwnd, rcvwnd)
-}
-
-// SetMtu sets the maximum transmission unit
-func (s *UDPSession) SetMtu(mtu int) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	s.kcp.SetMtu(mtu - s.headerSize)
-}
-
-// SetACKNoDelay changes ack flush option, set true to flush ack immediately,
-func (s *UDPSession) SetACKNoDelay(nodelay bool) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	s.ackNoDelay = nodelay
-}
-
-// SetNoDelay calls nodelay() of kcp
-func (s *UDPSession) SetNoDelay(nodelay, interval, resend, nc int) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	s.kcp.NoDelay(nodelay, interval, resend, nc)
-}
-
-// SetDSCP sets the DSCP field of IP header
-func (s *UDPSession) SetDSCP(tos int) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	if err := ipv4.NewConn(s.conn).SetTOS(tos << 2); err != nil {
-		log.Println("set tos:", err)
-	}
-}
-
-func (s *UDPSession) outputTask() {
-	// ping
-	ticker := time.NewTicker(5 * time.Second)
-	defer ticker.Stop()
-	for {
-		select {
-		case ext := <-s.chUDPOutput:
-			if s.block != nil {
-				io.ReadFull(crand.Reader, ext[:otpSize]) // OTP
-				checksum := crc32.ChecksumIEEE(ext[cryptHeaderSize:])
-				binary.LittleEndian.PutUint32(ext[otpSize:], checksum)
-				s.block.Encrypt(ext, ext)
-			}
-
-			//if rand.Intn(100) < 80 {
-			n, err := s.conn.WriteTo(ext, s.remote)
-			if err != nil {
-				log.Println(err, n)
-			}
-			//}
-
-		case <-ticker.C:
-			sz := rand.Intn(IKCP_MTU_DEF - s.headerSize - IKCP_OVERHEAD)
-			sz += s.headerSize + IKCP_OVERHEAD
-			ping := make([]byte, sz)
-			io.ReadFull(crand.Reader, ping)
-			if s.block != nil {
-				checksum := crc32.ChecksumIEEE(ping[cryptHeaderSize:])
-				binary.LittleEndian.PutUint32(ping[otpSize:], checksum)
-				s.block.Encrypt(ping, ping)
-			}
-
-			n, err := s.conn.WriteTo(ping, s.remote)
-			if err != nil {
-				log.Println(err, n)
-			}
-		case <-s.die:
-			return
-		}
-	}
-}
-
-// kcp update, input loop
-func (s *UDPSession) updateTask() {
-	var tc <-chan time.Time
-	if s.l == nil { // client
-		ticker := time.NewTicker(10 * time.Millisecond)
-		tc = ticker.C
-		defer ticker.Stop()
-	} else {
-		tc = s.chTicker
-	}
-
-	var nextupdate uint32
-	for {
-		select {
-		case <-tc:
-			s.mu.Lock()
-			current := currentMs()
-			if current >= nextupdate || s.needUpdate {
-				s.kcp.Update(current)
-				nextupdate = s.kcp.Check(current)
-			}
-			if s.kcp.WaitSnd() < int(s.kcp.snd_wnd) {
-				s.notifyWriteEvent()
-			}
-			s.needUpdate = false
-			s.mu.Unlock()
-		case <-s.die:
-			if s.l != nil { // has listener
-				s.l.chDeadlinks <- s.remote
-			}
-			return
-		}
-	}
-}
-
-// GetConv gets conversation id of a session
-func (s *UDPSession) GetConv() uint32 {
-	return s.kcp.conv
-}
-
-func (s *UDPSession) notifyReadEvent() {
-	select {
-	case s.chReadEvent <- struct{}{}:
-	default:
-	}
-}
-
-func (s *UDPSession) notifyWriteEvent() {
-	select {
-	case s.chWriteEvent <- struct{}{}:
-	default:
-	}
-}
-
-func (s *UDPSession) kcpInput(data []byte) {
-	now := time.Now()
-	if now.Sub(s.lastInputTs) > connTimeout {
-		s.Close()
-		return
-	}
-	s.lastInputTs = now
-
-	s.mu.Lock()
-	s.kcp.current = currentMs()
-	s.kcp.Input(data)
-
-	if s.ackNoDelay {
-		s.kcp.current = currentMs()
-		s.kcp.flush()
-	} else {
-		s.needUpdate = true
-	}
-	s.mu.Unlock()
-	s.notifyReadEvent()
-}
-
-func (s *UDPSession) receiver(ch chan []byte) {
-	for {
-		data := make([]byte, mtuLimit)
-		if n, _, err := s.conn.ReadFromUDP(data); err == nil && n >= s.headerSize+IKCP_OVERHEAD {
-			ch <- data[:n]
-		} else if err != nil {
-			return
-		}
-	}
-}
-
-// read loop for client session
-func (s *UDPSession) readLoop() {
-	chPacket := make(chan []byte, rxQueueLimit)
-	go s.receiver(chPacket)
-
-	for {
-		select {
-		case data := <-chPacket:
-			dataValid := false
-			if s.block != nil {
-				s.block.Decrypt(data, data)
-				data = data[otpSize:]
-				checksum := crc32.ChecksumIEEE(data[crcSize:])
-				if checksum == binary.LittleEndian.Uint32(data) {
-					data = data[crcSize:]
-					dataValid = true
-				}
-			} else if s.block == nil {
-				dataValid = true
-			}
-
-			if dataValid {
-				s.kcpInput(data)
-			}
-		case <-s.die:
-			return
-		}
-	}
-}
-
-type (
-	// Listener defines a server listening for connections
-	Listener struct {
-		block       BlockCrypt
-		conn        *net.UDPConn
-		sessions    map[string]*UDPSession
-		chAccepts   chan *UDPSession
-		chDeadlinks chan net.Addr
-		headerSize  int
-		die         chan struct{}
-	}
-
-	packet struct {
-		from *net.UDPAddr
-		data []byte
-	}
-)
-
-// monitor incoming data for all connections of server
-func (l *Listener) monitor() {
-	chPacket := make(chan packet, rxQueueLimit)
-	go l.receiver(chPacket)
-	ticker := time.NewTicker(10 * time.Millisecond)
-	defer ticker.Stop()
-	for {
-		select {
-		case p := <-chPacket:
-			data := p.data
-			from := p.from
-			dataValid := false
-			if l.block != nil {
-				l.block.Decrypt(data, data)
-				data = data[otpSize:]
-				checksum := crc32.ChecksumIEEE(data[crcSize:])
-				if checksum == binary.LittleEndian.Uint32(data) {
-					data = data[crcSize:]
-					dataValid = true
-				}
-			} else if l.block == nil {
-				dataValid = true
-			}
-
-			if dataValid {
-				addr := from.String()
-				s, ok := l.sessions[addr]
-				if !ok { // new session
-					var conv uint32
-					convValid := false
-
-					conv = binary.LittleEndian.Uint32(data)
-					convValid = true
-
-					if convValid {
-						s := newUDPSession(conv, l, l.conn, from, l.block)
-						s.kcpInput(data)
-						l.sessions[addr] = s
-						l.chAccepts <- s
-					}
-				} else {
-					s.kcpInput(data)
-				}
-			}
-		case deadlink := <-l.chDeadlinks:
-			delete(l.sessions, deadlink.String())
-		case <-l.die:
-			return
-		case <-ticker.C:
-			now := time.Now()
-			for _, s := range l.sessions {
-				select {
-				case s.chTicker <- now:
-				default:
-				}
-			}
-		}
-	}
-}
-
-func (l *Listener) receiver(ch chan packet) {
-	for {
-		data := make([]byte, mtuLimit)
-		if n, from, err := l.conn.ReadFromUDP(data); err == nil && n >= l.headerSize+IKCP_OVERHEAD {
-			ch <- packet{from, data[:n]}
-		} else if err != nil {
-			return
-		}
-	}
-}
-
-// Accept implements the Accept method in the Listener interface; it waits for the next call and returns a generic Conn.
-func (l *Listener) Accept() (*UDPSession, error) {
-	select {
-	case c := <-l.chAccepts:
-		return c, nil
-	case <-l.die:
-		return nil, errors.New("listener stopped")
-	}
-}
-
-// Close stops listening on the UDP address. Already Accepted connections are not closed.
-func (l *Listener) Close() error {
-	if err := l.conn.Close(); err == nil {
-		close(l.die)
-		return nil
-	} else {
-		return err
-	}
-}
-
-// Addr returns the listener's network address, The Addr returned is shared by all invocations of Addr, so do not modify it.
-func (l *Listener) Addr() net.Addr {
-	return l.conn.LocalAddr()
-}
-
-func currentMs() uint32 {
-	return uint32(time.Now().UnixNano() / int64(time.Millisecond))
-}
diff --git a/transport/internet/kcp/session.go b/transport/internet/kcp/session.go
deleted file mode 100644
index ef32dba2..00000000
--- a/transport/internet/kcp/session.go
+++ /dev/null
@@ -1,191 +0,0 @@
-package kcp
-
-import (
-	"errors"
-	"net"
-	"time"
-
-	v2net "github.com/v2ray/v2ray-core/common/net"
-	"github.com/v2ray/v2ray-core/transport/internet"
-)
-
-type KCPVlistener struct {
-	lst                    *Listener
-	previousSocketid       map[int]uint32
-	previousSocketid_mapid int
-}
-
-/*Accept Accept a KCP connection
-Since KCP is stateless, if package deliver after it was closed,
-It could be reconized as a new connection and call accept.
-If we can detect that the connection is of such a kind,
-we will discard that conn.
-*/
-func (kvl *KCPVlistener) Accept() (internet.Connection, error) {
-	conn, err := kvl.lst.Accept()
-	if err != nil {
-		return nil, err
-	}
-
-	if kvl.previousSocketid == nil {
-		kvl.previousSocketid = make(map[int]uint32)
-	}
-
-	var badbit bool = false
-
-	for _, key := range kvl.previousSocketid {
-		if key == conn.GetConv() {
-			badbit = true
-		}
-	}
-	if badbit {
-		conn.Close()
-		return nil, errors.New("KCP:ConnDup, Don't worry~")
-	} else {
-		kvl.previousSocketid_mapid++
-		kvl.previousSocketid[kvl.previousSocketid_mapid] = conn.GetConv()
-		/*
-			Here we assume that count(connection) < 512
-			This won't always true.
-			More work might be necessary to deal with this in a better way.
-		*/
-		if kvl.previousSocketid_mapid >= 512 {
-			delete(kvl.previousSocketid, kvl.previousSocketid_mapid-512)
-		}
-	}
-
-	kcv := &KCPVconn{hc: conn}
-	err = kcv.ApplyConf()
-	if err != nil {
-		return nil, err
-	}
-	return kcv, nil
-}
-
-func (kvl *KCPVlistener) Close() error {
-	return kvl.lst.Close()
-}
-
-func (kvl *KCPVlistener) Addr() net.Addr {
-	return kvl.lst.Addr()
-}
-
-type KCPVconn struct {
-	hc         *UDPSession
-	conntokeep time.Time
-}
-
-func (kcpvc *KCPVconn) Read(b []byte) (int, error) {
-	ifb := time.Now().Add(time.Duration(effectiveConfig.ReadTimeout) * time.Second)
-	if ifb.After(kcpvc.conntokeep) {
-		kcpvc.conntokeep = ifb
-	}
-	kcpvc.hc.SetDeadline(kcpvc.conntokeep)
-	return kcpvc.hc.Read(b)
-}
-
-func (kcpvc *KCPVconn) Write(b []byte) (int, error) {
-	ifb := time.Now().Add(time.Duration(effectiveConfig.WriteTimeout) * time.Second)
-	if ifb.After(kcpvc.conntokeep) {
-		kcpvc.conntokeep = ifb
-	}
-	kcpvc.hc.SetDeadline(kcpvc.conntokeep)
-	return kcpvc.hc.Write(b)
-}
-
-/*ApplyConf will apply kcpvc.conf to current Socket
-
-It is recommmanded to call this func once and only once
-*/
-func (kcpvc *KCPVconn) ApplyConf() error {
-	nodelay, interval, resend, nc := 0, 40, 0, 0
-	switch effectiveConfig.Mode {
-	case "normal":
-		nodelay, interval, resend, nc = 0, 30, 2, 1
-	case "fast":
-		nodelay, interval, resend, nc = 0, 20, 2, 1
-	case "fast2":
-		nodelay, interval, resend, nc = 1, 20, 2, 1
-	case "fast3":
-		nodelay, interval, resend, nc = 1, 10, 2, 1
-	}
-
-	kcpvc.hc.SetNoDelay(nodelay, interval, resend, nc)
-	kcpvc.hc.SetWindowSize(effectiveConfig.Sndwnd, effectiveConfig.Rcvwnd)
-	kcpvc.hc.SetMtu(effectiveConfig.Mtu)
-	kcpvc.hc.SetACKNoDelay(effectiveConfig.Acknodelay)
-	kcpvc.hc.SetDSCP(effectiveConfig.Dscp)
-	return nil
-}
-
-/*Close Close the current conn
-We have to delay the close of Socket for a few second
-or the VMess EOF can be too late to send.
-*/
-func (kcpvc *KCPVconn) Close() error {
-	go func() {
-		time.Sleep(2000 * time.Millisecond)
-		kcpvc.hc.Close()
-	}()
-	return nil
-}
-
-func (kcpvc *KCPVconn) LocalAddr() net.Addr {
-	return kcpvc.hc.LocalAddr()
-}
-
-func (kcpvc *KCPVconn) RemoteAddr() net.Addr {
-	return kcpvc.hc.RemoteAddr()
-}
-
-func (kcpvc *KCPVconn) SetDeadline(t time.Time) error {
-	return kcpvc.hc.SetDeadline(t)
-}
-
-func (kcpvc *KCPVconn) SetReadDeadline(t time.Time) error {
-	return kcpvc.hc.SetReadDeadline(t)
-}
-
-func (kcpvc *KCPVconn) SetWriteDeadline(t time.Time) error {
-	return kcpvc.hc.SetWriteDeadline(t)
-}
-
-func (this *KCPVconn) Reusable() bool {
-	return false
-}
-
-func (this *KCPVconn) SetReusable(b bool) {
-
-}
-
-func ListenKCP(address v2net.Address, port v2net.Port) (internet.Listener, error) {
-	conn, err := net.ListenUDP("udp", &net.UDPAddr{
-		IP:   address.IP(),
-		Port: int(port),
-	})
-	if err != nil {
-		return nil, err
-	}
-
-	block, _ := NewNoneBlockCrypt(nil)
-
-	l := new(Listener)
-	l.conn = conn
-	l.sessions = make(map[string]*UDPSession)
-	l.chAccepts = make(chan *UDPSession, 1024)
-	l.chDeadlinks = make(chan net.Addr, 1024)
-	l.die = make(chan struct{})
-	l.block = block
-
-	// caculate header size
-	if l.block != nil {
-		l.headerSize += cryptHeaderSize
-	}
-
-	go l.monitor()
-	return &KCPVlistener{lst: l}, nil
-}
-
-func init() {
-	internet.KCPListenFunc = ListenKCP
-}