diff --git a/common/bufio/bind.go b/common/bufio/bind.go
index caa5bbd..9788b4d 100644
--- a/common/bufio/bind.go
+++ b/common/bufio/bind.go
@@ -39,7 +39,7 @@ func (c *bindPacketConn) CreateReadWaiter() (N.ReadWaiter, bool) {
 	if !isReadWaiter {
 		return nil, false
 	}
-	return &BindPacketReadWaiter{readWaiter}, true
+	return &bindPacketReadWaiter{readWaiter}, true
 }
 
 func (c *bindPacketConn) RemoteAddr() net.Addr {
@@ -104,9 +104,62 @@ func (c *UnbindPacketConn) CreateReadWaiter() (N.PacketReadWaiter, bool) {
 	if !isReadWaiter {
 		return nil, false
 	}
-	return &UnbindPacketReadWaiter{readWaiter, c.addr}, true
+	return &unbindPacketReadWaiter{readWaiter, c.addr}, true
 }
 
 func (c *UnbindPacketConn) Upstream() any {
 	return c.ExtendedConn
 }
+
+func NewServerPacketConn(conn net.PacketConn) N.ExtendedConn {
+	return &serverPacketConn{
+		NetPacketConn: NewPacketConn(conn),
+	}
+}
+
+type serverPacketConn struct {
+	N.NetPacketConn
+	remoteAddr M.Socksaddr
+}
+
+func (c *serverPacketConn) Read(p []byte) (n int, err error) {
+	n, addr, err := c.NetPacketConn.ReadFrom(p)
+	if err != nil {
+		return
+	}
+	c.remoteAddr = M.SocksaddrFromNet(addr)
+	return
+}
+
+func (c *serverPacketConn) ReadBuffer(buffer *buf.Buffer) error {
+	destination, err := c.NetPacketConn.ReadPacket(buffer)
+	if err != nil {
+		return err
+	}
+	c.remoteAddr = destination
+	return nil
+}
+
+func (c *serverPacketConn) Write(p []byte) (n int, err error) {
+	return c.NetPacketConn.WriteTo(p, c.remoteAddr.UDPAddr())
+}
+
+func (c *serverPacketConn) WriteBuffer(buffer *buf.Buffer) error {
+	return c.NetPacketConn.WritePacket(buffer, c.remoteAddr)
+}
+
+func (c *serverPacketConn) RemoteAddr() net.Addr {
+	return c.remoteAddr
+}
+
+func (c *serverPacketConn) Upstream() any {
+	return c.NetPacketConn
+}
+
+func (c *serverPacketConn) CreateReadWaiter() (N.ReadWaiter, bool) {
+	readWaiter, isReadWaiter := CreatePacketReadWaiter(c.NetPacketConn)
+	if !isReadWaiter {
+		return nil, false
+	}
+	return &serverPacketReadWaiter{c, readWaiter}, true
+}
diff --git a/common/bufio/bind_wait.go b/common/bufio/bind_wait.go
index 1396552..779474c 100644
--- a/common/bufio/bind_wait.go
+++ b/common/bufio/bind_wait.go
@@ -6,33 +6,33 @@ import (
 	N "github.com/sagernet/sing/common/network"
 )
 
-var _ N.ReadWaiter = (*BindPacketReadWaiter)(nil)
+var _ N.ReadWaiter = (*bindPacketReadWaiter)(nil)
 
-type BindPacketReadWaiter struct {
+type bindPacketReadWaiter struct {
 	readWaiter N.PacketReadWaiter
 }
 
-func (w *BindPacketReadWaiter) InitializeReadWaiter(options N.ReadWaitOptions) (needCopy bool) {
+func (w *bindPacketReadWaiter) InitializeReadWaiter(options N.ReadWaitOptions) (needCopy bool) {
 	return w.readWaiter.InitializeReadWaiter(options)
 }
 
-func (w *BindPacketReadWaiter) WaitReadBuffer() (buffer *buf.Buffer, err error) {
+func (w *bindPacketReadWaiter) WaitReadBuffer() (buffer *buf.Buffer, err error) {
 	buffer, _, err = w.readWaiter.WaitReadPacket()
 	return
 }
 
-var _ N.PacketReadWaiter = (*UnbindPacketReadWaiter)(nil)
+var _ N.PacketReadWaiter = (*unbindPacketReadWaiter)(nil)
 
-type UnbindPacketReadWaiter struct {
+type unbindPacketReadWaiter struct {
 	readWaiter N.ReadWaiter
 	addr       M.Socksaddr
 }
 
-func (w *UnbindPacketReadWaiter) InitializeReadWaiter(options N.ReadWaitOptions) (needCopy bool) {
+func (w *unbindPacketReadWaiter) InitializeReadWaiter(options N.ReadWaitOptions) (needCopy bool) {
 	return w.readWaiter.InitializeReadWaiter(options)
 }
 
-func (w *UnbindPacketReadWaiter) WaitReadPacket() (buffer *buf.Buffer, destination M.Socksaddr, err error) {
+func (w *unbindPacketReadWaiter) WaitReadPacket() (buffer *buf.Buffer, destination M.Socksaddr, err error) {
 	buffer, err = w.readWaiter.WaitReadBuffer()
 	if err != nil {
 		return
@@ -40,3 +40,23 @@ func (w *UnbindPacketReadWaiter) WaitReadPacket() (buffer *buf.Buffer, destinati
 	destination = w.addr
 	return
 }
+
+var _ N.ReadWaiter = (*serverPacketReadWaiter)(nil)
+
+type serverPacketReadWaiter struct {
+	*serverPacketConn
+	readWaiter N.PacketReadWaiter
+}
+
+func (w *serverPacketReadWaiter) InitializeReadWaiter(options N.ReadWaitOptions) (needCopy bool) {
+	return w.readWaiter.InitializeReadWaiter(options)
+}
+
+func (w *serverPacketReadWaiter) WaitReadBuffer() (buffer *buf.Buffer, err error) {
+	buffer, destination, err := w.readWaiter.WaitReadPacket()
+	if err != nil {
+		return
+	}
+	w.remoteAddr = destination
+	return
+}
diff --git a/common/network/thread.go b/common/network/thread.go
index ac3ca69..22063af 100644
--- a/common/network/thread.go
+++ b/common/network/thread.go
@@ -154,15 +154,16 @@ type WriterWithMTU interface {
 
 func CalculateMTU(reader any, writer any) int {
 	readerMTU := calculateReaderMTU(reader)
-	readerHeadroom := calculateReaderFrontHeadroom(reader)
 	writerMTU := calculateWriterMTU(writer)
-	if readerMTU > writerMTU {
-		return readerMTU + readerHeadroom
-	}
-	if writerMTU > buf.BufferSize {
+	if readerMTU == 0 && writerMTU == 0 || readerMTU > buf.BufferSize || writerMTU > buf.BufferSize {
 		return 0
 	}
-	return writerMTU + readerHeadroom
+	readerHeadroom := calculateReaderFrontHeadroom(reader)
+	if readerMTU > writerMTU {
+		return readerMTU + readerHeadroom
+	} else {
+		return writerMTU + readerHeadroom
+	}
 }
 
 func calculateReaderMTU(reader any) int {
diff --git a/protocol/socks/handshake.go b/protocol/socks/handshake.go
index 2a2cecf..9e742a2 100644
--- a/protocol/socks/handshake.go
+++ b/protocol/socks/handshake.go
@@ -9,6 +9,7 @@ import (
 
 	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/auth"
+	"github.com/sagernet/sing/common/bufio"
 	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
@@ -219,7 +220,7 @@ func HandleConnection0(ctx context.Context, conn net.Conn, version byte, authent
 			metadata.Destination = request.Destination
 			var innerError error
 			done := make(chan struct{})
-			associatePacketConn := NewAssociatePacketConn(udpConn, request.Destination, conn)
+			associatePacketConn := NewAssociatePacketConn(bufio.NewServerPacketConn(udpConn), request.Destination, conn)
 			go func() {
 				innerError = handler.NewPacketConnection(ctx, associatePacketConn, metadata)
 				close(done)