diff --git a/transport/internet/kcp/connection.go b/transport/internet/kcp/connection.go
index 25fec1979..88d7d05a3 100644
--- a/transport/internet/kcp/connection.go
+++ b/transport/internet/kcp/connection.go
@@ -38,7 +38,7 @@ const (
 	StatePeerClosed      State = 2 // Connection is closed on remote
 	StateTerminating     State = 3 // Connection is ready to be destroyed locally
 	StatePeerTerminating State = 4 // Connection is ready to be destroyed on remote
-	StateTerminated      State = 5 // Connection is detroyed.
+	StateTerminated      State = 5 // Connection is destroyed.
 )
 
 func nowMillisec() int64 {
@@ -137,21 +137,21 @@ func NewUpdater(interval uint32, shouldContinue predicate.Predicate, shouldTermi
 	return u
 }
 
-func (v *Updater) WakeUp() {
+func (u *Updater) WakeUp() {
 	select {
-	case v.notifier <- true:
+	case u.notifier <- true:
 	default:
 	}
 }
 
-func (v *Updater) Run() {
-	for <-v.notifier {
-		if v.shouldTerminate() {
+func (u *Updater) Run() {
+	for <-u.notifier {
+		if u.shouldTerminate() {
 			return
 		}
-		interval := v.Interval()
-		for v.shouldContinue() {
-			v.updateFunc()
+		interval := u.Interval()
+		for u.shouldContinue() {
+			u.updateFunc()
 			time.Sleep(interval)
 		}
 	}
@@ -280,24 +280,36 @@ func (v *Connection) ReadMultiBuffer() (buf.MultiBuffer, error) {
 			return nil, io.EOF
 		}
 
-		duration := time.Minute
-		if !v.rd.IsZero() {
-			duration = time.Until(v.rd)
-			if duration < 0 {
-				return nil, ErrIOTimeout
-			}
-		}
-
-		select {
-		case <-v.dataInput:
-		case <-time.After(duration):
-			if !v.rd.IsZero() && v.rd.Before(time.Now()) {
-				return nil, ErrIOTimeout
-			}
+		if err := v.waitForDataInput(); err != nil {
+			return nil, err
 		}
 	}
 }
 
+func (v *Connection) waitForDataInput() error {
+	if v.State() == StatePeerTerminating {
+		return io.EOF
+	}
+
+	duration := time.Minute
+	if !v.rd.IsZero() {
+		duration = time.Until(v.rd)
+		if duration < 0 {
+			return ErrIOTimeout
+		}
+	}
+
+	select {
+	case <-v.dataInput:
+	case <-time.After(duration):
+		if !v.rd.IsZero() && v.rd.Before(time.Now()) {
+			return ErrIOTimeout
+		}
+	}
+
+	return nil
+}
+
 // Read implements the Conn Read method.
 func (v *Connection) Read(b []byte) (int, error) {
 	if v == nil {
@@ -313,28 +325,32 @@ func (v *Connection) Read(b []byte) (int, error) {
 			return nBytes, nil
 		}
 
-		if v.State() == StatePeerTerminating {
-			return 0, io.EOF
-		}
-
-		duration := time.Minute
-		if !v.rd.IsZero() {
-			duration = time.Until(v.rd)
-			if duration < 0 {
-				return 0, ErrIOTimeout
-			}
-		}
-
-		select {
-		case <-v.dataInput:
-		case <-time.After(duration):
-			if !v.rd.IsZero() && v.rd.Before(time.Now()) {
-				return 0, ErrIOTimeout
-			}
+		if err := v.waitForDataInput(); err != nil {
+			return 0, err
 		}
 	}
 }
 
+func (v *Connection) waitForDataOutput() error {
+	duration := time.Minute
+	if !v.wd.IsZero() {
+		duration = time.Until(v.wd)
+		if duration < 0 {
+			return ErrIOTimeout
+		}
+	}
+
+	select {
+	case <-v.dataOutput:
+	case <-time.After(duration):
+		if !v.wd.IsZero() && v.wd.Before(time.Now()) {
+			return ErrIOTimeout
+		}
+	}
+
+	return nil
+}
+
 // Write implements io.Writer.
 func (v *Connection) Write(b []byte) (int, error) {
 	totalWritten := 0
@@ -359,20 +375,8 @@ func (v *Connection) Write(b []byte) (int, error) {
 			}
 		}
 
-		duration := time.Minute
-		if !v.wd.IsZero() {
-			duration = time.Until(v.wd)
-			if duration < 0 {
-				return totalWritten, ErrIOTimeout
-			}
-		}
-
-		select {
-		case <-v.dataOutput:
-		case <-time.After(duration):
-			if !v.wd.IsZero() && v.wd.Before(time.Now()) {
-				return totalWritten, ErrIOTimeout
-			}
+		if err := v.waitForDataOutput(); err != nil {
+			return totalWritten, err
 		}
 	}
 }
@@ -400,20 +404,8 @@ func (v *Connection) WriteMultiBuffer(mb buf.MultiBuffer) error {
 			}
 		}
 
-		duration := time.Minute
-		if !v.wd.IsZero() {
-			duration = time.Until(v.wd)
-			if duration < 0 {
-				return ErrIOTimeout
-			}
-		}
-
-		select {
-		case <-v.dataOutput:
-		case <-time.After(duration):
-			if !v.wd.IsZero() && v.wd.Before(time.Now()) {
-				return ErrIOTimeout
-			}
+		if err := v.waitForDataOutput(); err != nil {
+			return err
 		}
 	}
 }