diff --git a/cmd/ck-server/ck-server.go b/cmd/ck-server/ck-server.go
index c4d76ff..2485fe2 100644
--- a/cmd/ck-server/ck-server.go
+++ b/cmd/ck-server/ck-server.go
@@ -9,7 +9,7 @@ import (
 	"net/http"
 	_ "net/http/pprof"
 	"os"
-	//"runtime"
+	"runtime"
 	"strings"
 	"time"
 
@@ -115,7 +115,12 @@ func dispatchConnection(conn net.Conn, sta *server.State) {
 				newStream, err := sesh.AcceptStream()
 				if err != nil {
 					log.Printf("Failed to get new stream: %v", err)
-					continue
+					if err == mux.ErrBrokenSession {
+						sta.DelSession(arrSID)
+						return
+					} else {
+						continue
+					}
 				}
 				ssConn, err := net.Dial("tcp", sta.SS_LOCAL_HOST+":"+sta.SS_LOCAL_PORT)
 				if err != nil {
@@ -131,6 +136,7 @@ func dispatchConnection(conn net.Conn, sta *server.State) {
 }
 
 func main() {
+	runtime.SetBlockProfileRate(5)
 	go func() {
 		log.Println(http.ListenAndServe("0.0.0.0:8001", nil))
 	}()
diff --git a/internal/multiplex/frameSorter.go b/internal/multiplex/frameSorter.go
index e4a658b..d858dc3 100644
--- a/internal/multiplex/frameSorter.go
+++ b/internal/multiplex/frameSorter.go
@@ -56,7 +56,12 @@ func (sh *sorterHeap) Pop() interface{} {
 
 func (s *Stream) recvNewFrame() {
 	for {
-		f := <-s.newFrameCh
+		var f *Frame
+		select {
+		case <-s.die:
+			return
+		case f = <-s.newFrameCh:
+		}
 		if f == nil {
 			log.Println("nil frame")
 			continue
diff --git a/internal/multiplex/session.go b/internal/multiplex/session.go
index 49a029e..af7adb7 100644
--- a/internal/multiplex/session.go
+++ b/internal/multiplex/session.go
@@ -9,14 +9,15 @@ import (
 )
 
 const (
-	errBrokenSession        = "broken session"
-	errRepeatSessionClosing = "trying to close a closed session"
 	// Copied from smux
 	acceptBacklog = 1024
 
 	closeBacklog = 512
 )
 
+var ErrBrokenSession = errors.New("broken session")
+var errRepeatSessionClosing = errors.New("trying to close a closed session")
+
 type Session struct {
 	id int
 
@@ -58,6 +59,7 @@ func MakeSession(id int, conn net.Conn, obfs func(*Frame) []byte, deobfs func([]
 		streams:      make(map[uint32]*Stream),
 		acceptCh:     make(chan *Stream, acceptBacklog),
 		closeQCh:     make(chan uint32, closeBacklog),
+		die:          make(chan struct{}),
 	}
 	sesh.sb = makeSwitchboard(conn, sesh)
 	return sesh
@@ -80,7 +82,7 @@ func (sesh *Session) OpenStream() (*Stream, error) {
 func (sesh *Session) AcceptStream() (*Stream, error) {
 	select {
 	case <-sesh.die:
-		return nil, errors.New(errBrokenSession)
+		return nil, ErrBrokenSession
 	case stream := <-sesh.acceptCh:
 		return stream, nil
 	}
@@ -122,7 +124,7 @@ func (sesh *Session) Close() error {
 	sesh.closingM.Lock()
 	defer sesh.closingM.Unlock()
 	if sesh.closing {
-		return errors.New(errRepeatSessionClosing)
+		return errRepeatSessionClosing
 	}
 	sesh.closing = true
 	close(sesh.die)
@@ -138,6 +140,7 @@ func (sesh *Session) Close() error {
 	}
 	sesh.streamsM.Unlock()
 
+	close(sesh.sb.die)
 	return nil
 
 }
diff --git a/internal/multiplex/stream.go b/internal/multiplex/stream.go
index 768e895..5479fed 100644
--- a/internal/multiplex/stream.go
+++ b/internal/multiplex/stream.go
@@ -7,10 +7,8 @@ import (
 	"sync/atomic"
 )
 
-const (
-	errBrokenStream        = "broken stream"
-	errRepeatStreamClosing = "trying to close a closed stream"
-)
+var errBrokenStream = errors.New("broken stream")
+var errRepeatStreamClosing = errors.New("trying to close a closed stream")
 
 type Stream struct {
 	id uint32
@@ -23,14 +21,18 @@ type Stream struct {
 	sh          sorterHeap
 	wrapMode    bool
 
-	newFrameCh  chan *Frame
+	// New frames are received through newFrameCh by frameSorter
+	newFrameCh chan *Frame
+	// sortedBufCh are order-sorted data ready to be read raw
 	sortedBufCh chan []byte
 
 	nextSendSeq uint32
 
 	closingM sync.Mutex
-	die      chan struct{}
-	closing  bool
+	// close(die) is used to notify different goroutines that this stream is closing
+	die chan struct{}
+	// to prevent closing a closed channel
+	closing bool
 }
 
 func makeStream(id uint32, sesh *Session) *Stream {
@@ -51,7 +53,7 @@ func (stream *Stream) Read(buf []byte) (n int, err error) {
 		select {
 		case <-stream.die:
 			log.Printf("Stream %v dying\n", stream.id)
-			return 0, errors.New(errBrokenStream)
+			return 0, errBrokenStream
 		default:
 			return 0, nil
 		}
@@ -59,7 +61,7 @@ func (stream *Stream) Read(buf []byte) (n int, err error) {
 	select {
 	case <-stream.die:
 		log.Printf("Stream %v dying\n", stream.id)
-		return 0, errors.New(errBrokenStream)
+		return 0, errBrokenStream
 	case data := <-stream.sortedBufCh:
 		if len(buf) < len(data) {
 			log.Println(len(data))
@@ -75,7 +77,7 @@ func (stream *Stream) Write(in []byte) (n int, err error) {
 	select {
 	case <-stream.die:
 		log.Printf("Stream %v dying\n", stream.id)
-		return 0, errors.New(errBrokenStream)
+		return 0, errBrokenStream
 	default:
 	}
 
@@ -109,7 +111,7 @@ func (stream *Stream) Close() error {
 	stream.closingM.Lock()
 	defer stream.closingM.Unlock()
 	if stream.closing {
-		return errors.New(errRepeatStreamClosing)
+		return errRepeatStreamClosing
 	}
 	stream.closing = true
 	close(stream.die)
@@ -127,7 +129,7 @@ func (stream *Stream) closeNoDelMap() error {
 	stream.closingM.Lock()
 	defer stream.closingM.Unlock()
 	if stream.closing {
-		return errors.New(errRepeatStreamClosing)
+		return errRepeatStreamClosing
 	}
 	stream.closing = true
 	close(stream.die)
diff --git a/internal/multiplex/switchboard.go b/internal/multiplex/switchboard.go
index 3d5808c..a1c7f99 100644
--- a/internal/multiplex/switchboard.go
+++ b/internal/multiplex/switchboard.go
@@ -20,9 +20,12 @@ type switchboard struct {
 
 	// For telling dispatcher how many bytes have been sent after Connection.send.
 	sentNotifyCh chan *sentNotifier
-	dispatCh     chan []byte
-	newConnCh    chan net.Conn
-	closingCECh  chan *connEnclave
+	// dispatCh is used by streams to send new data to remote
+	dispatCh    chan []byte
+	newConnCh   chan net.Conn
+	closingCECh chan *connEnclave
+	die         chan struct{}
+	closing     bool
 }
 
 // Some data comes from a Stream to be sent through one of the many
@@ -57,6 +60,7 @@ func makeSwitchboard(conn net.Conn, sesh *Session) *switchboard {
 		dispatCh:     make(chan []byte, dispatchBacklog),
 		newConnCh:    make(chan net.Conn, newConnBacklog),
 		closingCECh:  make(chan *connEnclave, 5),
+		die:          make(chan struct{}),
 	}
 	ce := &connEnclave{
 		sb:         sb,
@@ -97,6 +101,7 @@ func (ce *connEnclave) send(data []byte) {
 // Dispatcher sends data coming from a stream to a remote connection
 // I used channels here because I didn't want to use mutex
 func (sb *switchboard) dispatch() {
+	var dying bool
 	for {
 		select {
 		// dispatCh receives data from stream.Write
@@ -123,6 +128,15 @@ func (sb *switchboard) dispatch() {
 					break
 				}
 			}
+			if len(sb.ces) == 0 && !dying {
+				sb.session.Close()
+			}
+		case <-sb.die:
+			dying = true
+			for _, ce := range sb.ces {
+				ce.remoteConn.Close()
+			}
+			return
 		}
 	}
 }
diff --git a/internal/server/state.go b/internal/server/state.go
index 8f564bb..7971b8b 100644
--- a/internal/server/state.go
+++ b/internal/server/state.go
@@ -116,8 +116,8 @@ func (sta *State) ParseConfig(conf string) (err error) {
 }
 
 func (sta *State) GetSession(SID [32]byte) *mux.Session {
-	sta.sessionsM.Lock()
-	defer sta.sessionsM.Unlock()
+	sta.sessionsM.RLock()
+	defer sta.sessionsM.RUnlock()
 	if sesh, ok := sta.sessions[SID]; ok {
 		return sesh
 	} else {
@@ -131,6 +131,12 @@ func (sta *State) PutSession(SID [32]byte, sesh *mux.Session) {
 	sta.sessionsM.Unlock()
 }
 
+func (sta *State) DelSession(SID [32]byte) {
+	sta.sessionsM.Lock()
+	delete(sta.sessions, SID)
+	sta.sessionsM.Unlock()
+}
+
 func (sta *State) getUsedRandom(random [32]byte) int {
 	sta.usedRandomM.Lock()
 	defer sta.usedRandomM.Unlock()