diff --git a/app/proxyman/inbound/worker.go b/app/proxyman/inbound/worker.go
index 8a8194673..c3f72b00c 100644
--- a/app/proxyman/inbound/worker.go
+++ b/app/proxyman/inbound/worker.go
@@ -124,6 +124,32 @@ func (c *udpConn) updateActivity() {
 	atomic.StoreInt64(&c.lastActivityTime, time.Now().Unix())
 }
 
+// ReadMultiBuffer implements buf.Reader
+func (c *udpConn) ReadMultiBuffer() (buf.MultiBuffer, error) {
+	var payload buf.MultiBuffer
+
+	select {
+	case in := <-c.input:
+		payload.Append(in)
+	case <-c.done.Wait():
+		return nil, io.EOF
+	}
+
+L:
+	for {
+		select {
+		case in := <-c.input:
+			payload.Append(in)
+		case <-c.done.Wait():
+			break L
+		default:
+			break L
+		}
+	}
+
+	return payload, nil
+}
+
 func (c *udpConn) Read(buf []byte) (int, error) {
 	select {
 	case in := <-c.input:
@@ -202,7 +228,7 @@ func (w *udpWorker) getConnection(id connID) (*udpConn, bool) {
 	w.Lock()
 	defer w.Unlock()
 
-	if conn, found := w.activeConn[id]; found {
+	if conn, found := w.activeConn[id]; found && !conn.done.Done() {
 		return conn, true
 	}
 
diff --git a/app/proxyman/mux/frame.go b/app/proxyman/mux/frame.go
index 8b78846d5..ba43d19b5 100644
--- a/app/proxyman/mux/frame.go
+++ b/app/proxyman/mux/frame.go
@@ -1,6 +1,7 @@
 package mux
 
 import (
+	"v2ray.com/core/common"
 	"v2ray.com/core/common/bitmask"
 	"v2ray.com/core/common/buf"
 	"v2ray.com/core/common/net"
@@ -58,21 +59,21 @@ type FrameMetadata struct {
 
 func (f FrameMetadata) WriteTo(b *buf.Buffer) error {
 	lenBytes := b.Bytes()
-	b.AppendBytes(0x00, 0x00)
+	common.Must2(b.AppendBytes(0x00, 0x00))
 
 	len0 := b.Len()
 	if err := b.AppendSupplier(serial.WriteUint16(f.SessionID)); err != nil {
 		return err
 	}
 
-	b.AppendBytes(byte(f.SessionStatus), byte(f.Option))
+	common.Must2(b.AppendBytes(byte(f.SessionStatus), byte(f.Option)))
 
 	if f.SessionStatus == SessionStatusNew {
 		switch f.Target.Network {
 		case net.Network_TCP:
-			b.AppendBytes(byte(TargetNetworkTCP))
+			common.Must2(b.AppendBytes(byte(TargetNetworkTCP)))
 		case net.Network_UDP:
-			b.AppendBytes(byte(TargetNetworkUDP))
+			common.Must2(b.AppendBytes(byte(TargetNetworkUDP)))
 		}
 
 		if err := addrParser.WriteAddressPort(b, f.Target.Address, f.Target.Port); err != nil {
@@ -85,6 +86,8 @@ func (f FrameMetadata) WriteTo(b *buf.Buffer) error {
 	return nil
 }
 
+// ReadFrameFrom reads a FrameMetadata from the given buffer.
+// Visible for testing only.
 func ReadFrameFrom(b *buf.Buffer) (*FrameMetadata, error) {
 	if b.Len() < 4 {
 		return nil, newError("insufficient buffer: ", b.Len())