diff --git a/client/main.go b/client/main.go
index 5d5ec15..9bae33a 100644
--- a/client/main.go
+++ b/client/main.go
@@ -20,16 +20,20 @@ import (
 	smuxv2 "github.com/xtaci/smux/v2"
 )
 
-// SALT is use for pbkdf2 key expansion
-const SALT = "kcp-go"
-
-// maximum supported smux version
-const maxSmuxVer = 2
+const (
+	// SALT is use for pbkdf2 key expansion
+	SALT = "kcp-go"
+	// maximum supported smux version
+	maxSmuxVer = 2
+	// stream copy buffer size
+	bufSize = 32768
+)
 
 // VERSION is injected by buildflags
 var VERSION = "SELFBUILD"
 
-func handleClient(mux generic.Mux, p1 net.Conn, quiet bool) {
+// handleClient aggregates connection p1 on mux with 'writeLock'
+func handleClient(mux generic.Mux, p1 net.Conn, ctrl *generic.CopyControl, quiet bool) {
 	logln := func(v ...interface{}) {
 		if !quiet {
 			log.Println(v...)
@@ -53,7 +57,7 @@ func handleClient(mux generic.Mux, p1 net.Conn, quiet bool) {
 	streamCopy := func(dst io.Writer, src io.ReadCloser) chan struct{} {
 		die := make(chan struct{})
 		go func() {
-			if _, err := generic.Copy(dst, src); err != nil {
+			if _, err := generic.Copy(dst, src, ctrl); err != nil {
 				if s2, ok := p2.(generic.Stream); ok {
 					// verbose error handling
 					cause := err
@@ -455,11 +459,13 @@ func main() {
 		muxes := make([]struct {
 			session generic.Mux
 			ttl     time.Time
+			ctrl    *generic.CopyControl // for control of memory in copying
 		}, numconn)
 
 		for k := range muxes {
 			muxes[k].session = waitConn()
 			muxes[k].ttl = time.Now().Add(time.Duration(config.AutoExpire) * time.Second)
+			muxes[k].ctrl = &generic.CopyControl{Buffer: make([]byte, bufSize)}
 		}
 
 		chScavenger := make(chan generic.Mux, 128)
@@ -478,9 +484,10 @@ func main() {
 				chScavenger <- muxes[idx].session
 				muxes[idx].session = waitConn()
 				muxes[idx].ttl = time.Now().Add(time.Duration(config.AutoExpire) * time.Second)
+				muxes[idx].ctrl = &generic.CopyControl{Buffer: make([]byte, bufSize)}
 			}
 
-			go handleClient(muxes[idx].session, p1, config.Quiet)
+			go handleClient(muxes[idx].session, p1, muxes[idx].ctrl, config.Quiet)
 			rr++
 		}
 	}
diff --git a/generic/copy.go b/generic/copy.go
index 8a1105a..2964dcb 100644
--- a/generic/copy.go
+++ b/generic/copy.go
@@ -1,9 +1,20 @@
 package generic
 
-import "io"
+import (
+	"io"
+	"net"
+	"sync"
+)
 
-// Memory optimized Copy function specified for this library
-func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
+const bufSize = 4096
+
+type CopyControl struct {
+	Buffer []byte // shared buffer for copying controlled by mutex
+	sync.Mutex
+}
+
+// Memory optimized io.Copy function specified for this library
+func Copy(dst io.Writer, src io.Reader, ctrl *CopyControl) (written int64, err error) {
 	// If the reader has a WriteTo method, use it to do the copy.
 	// Avoids an allocation and a copy.
 	if wt, ok := src.(io.WriterTo); ok {
@@ -14,39 +25,16 @@ func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
 		return rt.ReadFrom(src)
 	}
 
-	// limited to 4K per stream
-	size := 4096
-	if l, ok := src.(*io.LimitedReader); ok && int64(size) > l.N {
-		if l.N < 1 {
-			size = 1
-		} else {
-			size = int(l.N)
+	// if src is net.TCPConn, and dst is a multiplexed connection
+	// reading can be controlled by writable events of smux
+	// and make the reading serialized
+	if tcpconn, ok := src.(*net.TCPConn); ok {
+		if ctrl != nil {
+			return rawCopy(dst, tcpconn, ctrl)
 		}
 	}
-	buf := make([]byte, size)
 
-	for {
-		nr, er := src.Read(buf)
-		if nr > 0 {
-			nw, ew := dst.Write(buf[0:nr])
-			if nw > 0 {
-				written += int64(nw)
-			}
-			if ew != nil {
-				err = ew
-				break
-			}
-			if nr != nw {
-				err = io.ErrShortWrite
-				break
-			}
-		}
-		if er != nil {
-			if er != io.EOF {
-				err = er
-			}
-			break
-		}
-	}
-	return written, err
+	// fallback to standard io.CopyBuffer
+	buf := make([]byte, bufSize)
+	return io.CopyBuffer(dst, src, buf)
 }
diff --git a/generic/rawcopy_unix.go b/generic/rawcopy_unix.go
new file mode 100644
index 0000000..c7f7ff6
--- /dev/null
+++ b/generic/rawcopy_unix.go
@@ -0,0 +1,68 @@
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package generic
+
+import (
+	"io"
+	"net"
+
+	"syscall"
+)
+
+func rawCopy(dst io.Writer, src *net.TCPConn, ctrl *CopyControl) (written int64, err error) {
+	c, err := src.SyscallConn()
+	if err != nil {
+		return 0, err
+	}
+
+	buf := ctrl.Buffer
+	for {
+		var er error
+		var nr int
+		rr := c.Read(func(s uintptr) bool {
+			ctrl.Lock() // writelock will block reading
+			defer ctrl.Unlock()
+			nr, er = syscall.Read(int(s), buf)
+			if er == syscall.EAGAIN {
+				return false
+			}
+			return true
+		})
+
+		// read EOF
+		if nr == 0 && er == nil {
+			break
+		}
+
+		if nr > 0 {
+			ctrl.Lock()
+			nw, ew := dst.Write(buf[0:nr])
+			ctrl.Unlock()
+			if nw > 0 {
+				written += int64(nw)
+			}
+			if ew != nil {
+				err = ew
+				break
+			}
+			if nr != nw {
+				err = io.ErrShortWrite
+				break
+			}
+		}
+		if er != nil {
+			if er != io.EOF {
+				err = er
+			}
+			break
+		}
+		if rr != nil {
+			if rr != io.EOF {
+				err = rr
+			}
+			break
+		}
+	}
+
+	return written, err
+}
diff --git a/generic/rawcopy_windows.go b/generic/rawcopy_windows.go
new file mode 100644
index 0000000..aea9686
--- /dev/null
+++ b/generic/rawcopy_windows.go
@@ -0,0 +1,71 @@
+// +build windows
+
+package generic
+
+import (
+	"io"
+	"net"
+	"syscall"
+)
+
+func rawCopy(dst io.Writer, src *net.TCPConn, ctrl *CopyControl) (written int64, err error) {
+	c, err := src.SyscallConn()
+	if err != nil {
+		return 0, err
+	}
+
+	buf := ctrl.Buffer
+	for {
+		var er error
+		var nr int
+		rr := c.Read(func(s uintptr) bool {
+			ctrl.Lock()
+			defer ctrl.Unlock()
+			var read uint32
+			var flags uint32
+			var wsabuf syscall.WSABuf
+			wsabuf.Buf = &buf[0]
+			wsabuf.Len = uint32(len(buf))
+			er = syscall.WSARecv(syscall.Handle(s), &wsabuf, 1, &read, &flags, nil, nil)
+			nr = int(read)
+			return true
+		})
+
+		// read EOF
+		if nr == 0 && er == nil {
+			break
+		}
+
+		if nr > 0 {
+			ctrl.Lock()
+			nw, ew := dst.Write(buf[0:nr])
+			ctrl.Unlock()
+			buf = nil
+			if nw > 0 {
+				written += int64(nw)
+			}
+			if ew != nil {
+				err = ew
+				break
+			}
+			if nr != nw {
+				err = io.ErrShortWrite
+				break
+			}
+		}
+		if er != nil {
+			if er != io.EOF {
+				err = er
+			}
+			break
+		}
+		if rr != nil {
+			if rr != io.EOF {
+				err = rr
+			}
+			break
+		}
+	}
+
+	return written, err
+}
diff --git a/go.sum b/go.sum
index f483ce9..36bea71 100644
--- a/go.sum
+++ b/go.sum
@@ -19,36 +19,12 @@ github.com/tjfoc/gmsm v1.0.1 h1:R11HlqhXkDospckjZEihx9SW/2VW0RgdwrykyWMFOQU=
 github.com/tjfoc/gmsm v1.0.1/go.mod h1:XxO4hdhhrzAd+G4CjDqaOkd0hUzmtPR/d3EiBBMn/wc=
 github.com/urfave/cli v1.21.0 h1:wYSSj06510qPIzGSua9ZqsncMmWE3Zr55KBERygyrxE=
 github.com/urfave/cli v1.21.0/go.mod h1:lxDj6qX9Q6lWQxIrbrT0nwecwUtRnhVZAJjJZrVUZZQ=
-github.com/xtaci/kcp-go v5.4.13+incompatible h1:s6ba2XTw8lAj+s6AQNob25dCvWDgwE+U1QpEVBUoYy8=
-github.com/xtaci/kcp-go v5.4.13+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
-github.com/xtaci/kcp-go v5.4.14+incompatible h1:kQZr/ngKQtYrgXSUxwF4A59mTMzUp0BDmtWIRuXYoqg=
-github.com/xtaci/kcp-go v5.4.14+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
-github.com/xtaci/kcp-go v5.4.15+incompatible h1:QLDulPaKjT4k4cGeviyC1mt00gwJ3r5epx8yCw6ACEc=
-github.com/xtaci/kcp-go v5.4.15+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
-github.com/xtaci/kcp-go v5.4.16+incompatible h1:/L7UP4P4H/oXpMnrb2W9oOxCMVpjPi3FJeMJmgN+SUE=
-github.com/xtaci/kcp-go v5.4.16+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
-github.com/xtaci/kcp-go v5.4.17+incompatible h1:RudP76JCx062JSxPxSjBl+457+fS0M7T8zEZPLpC0o8=
-github.com/xtaci/kcp-go v5.4.17+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
-github.com/xtaci/kcp-go v5.4.18+incompatible h1:zxzRP8V54vhJ8QAKEjf1b9g96R01prybCRchx6rEmtg=
-github.com/xtaci/kcp-go v5.4.18+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
 github.com/xtaci/kcp-go v5.4.19+incompatible h1:vv7Ar1D9WZGiv6deIOluxrC26Oin/2jFtx8sFU5tlvw=
 github.com/xtaci/kcp-go v5.4.19+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
 github.com/xtaci/lossyconn v0.0.0-20190602105132-8df528c0c9ae h1:J0GxkO96kL4WF+AIT3M4mfUVinOCPgf2uUWYFUzN0sM=
 github.com/xtaci/lossyconn v0.0.0-20190602105132-8df528c0c9ae/go.mod h1:gXtu8J62kEgmN++bm9BVICuT/e8yiLI2KFobd/TRFsE=
-github.com/xtaci/smux v1.4.4 h1:FukIfahko+KHhS9Gxppkp6756opZymvPOLNmpny1is4=
-github.com/xtaci/smux v1.4.4/go.mod h1:LuA3S0xssf4fmGRJ7ow3EehgmDUzib4EcobaFNKvlMA=
-github.com/xtaci/smux v1.4.5 h1:Pi64WSFFIDrpMSzRZzqt5e4YO/m4a6BAKGjxSa+KU0A=
-github.com/xtaci/smux v1.4.5/go.mod h1:LuA3S0xssf4fmGRJ7ow3EehgmDUzib4EcobaFNKvlMA=
 github.com/xtaci/smux v1.4.6 h1:p9e/qj3Bj0zUT8qJWdmAZfmx5lOcZh0vLL0bQ8jnA7M=
 github.com/xtaci/smux v1.4.6/go.mod h1:LuA3S0xssf4fmGRJ7ow3EehgmDUzib4EcobaFNKvlMA=
-github.com/xtaci/smux/v2 v2.0.11 h1:thVWmgGRciZ8iaATwpY2B/51aHzmMI6wrF7DfcJSckU=
-github.com/xtaci/smux/v2 v2.0.11/go.mod h1:Iqy5a3Gax2p7WCKHOHkSNo/COthNFXd3/vqrcKNtzqI=
-github.com/xtaci/smux/v2 v2.0.13 h1:T3VtVS8CQ2nbsMttkzTB48acij5HAhi8x8gYe9SodJA=
-github.com/xtaci/smux/v2 v2.0.13/go.mod h1:Iqy5a3Gax2p7WCKHOHkSNo/COthNFXd3/vqrcKNtzqI=
-github.com/xtaci/smux/v2 v2.0.14 h1:XfmTsDX7lNTLPP8bCLRQuviP1AEix3NYefM/QVUg5X4=
-github.com/xtaci/smux/v2 v2.0.14/go.mod h1:Iqy5a3Gax2p7WCKHOHkSNo/COthNFXd3/vqrcKNtzqI=
-github.com/xtaci/smux/v2 v2.0.15 h1:dD4yV48m6ntMVV0mieHXkxwFdx2VYnjJpqqGElXVkTs=
-github.com/xtaci/smux/v2 v2.0.15/go.mod h1:Iqy5a3Gax2p7WCKHOHkSNo/COthNFXd3/vqrcKNtzqI=
 github.com/xtaci/smux/v2 v2.0.16 h1:2pGGbkFKTaMHIctYaovpwRpgdwWYy/6ZPaOQo00VW08=
 github.com/xtaci/smux/v2 v2.0.16/go.mod h1:Iqy5a3Gax2p7WCKHOHkSNo/COthNFXd3/vqrcKNtzqI=
 github.com/xtaci/tcpraw v1.2.25 h1:VDlqo0op17JeXBM6e2G9ocCNLOJcw9mZbobMbJjo0vk=
diff --git a/server/main.go b/server/main.go
index 5aff7ae..3feba5f 100644
--- a/server/main.go
+++ b/server/main.go
@@ -23,11 +23,14 @@ import (
 	"github.com/xtaci/tcpraw"
 )
 
-// SALT is use for pbkdf2 key expansion
-const SALT = "kcp-go"
-
-// maximum supported smux version
-const maxSmuxVer = 2
+const (
+	// SALT is use for pbkdf2 key expansion
+	SALT = "kcp-go"
+	// maximum supported smux version
+	maxSmuxVer = 2
+	// stream copy buffer size
+	bufSize = 32768
+)
 
 // VERSION is injected by buildflags
 var VERSION = "SELFBUILD"
@@ -73,6 +76,9 @@ func handleMux(conn net.Conn, config *Config) {
 		panic("incorrect smux version")
 	}
 
+	// copy to stream control
+	copyControl := &generic.CopyControl{Buffer: make([]byte, bufSize)}
+
 	for {
 		stream, err := muxer.Accept()
 		if err != nil {
@@ -94,12 +100,12 @@ func handleMux(conn net.Conn, config *Config) {
 				p1.Close()
 				return
 			}
-			handleClient(p1, p2, config.Quiet)
+			handleClient(p1, p2, copyControl, config.Quiet)
 		}(stream)
 	}
 }
 
-func handleClient(p1 io.ReadWriteCloser, p2 net.Conn, quiet bool) {
+func handleClient(p1 io.ReadWriteCloser, p2 net.Conn, ctrl *generic.CopyControl, quiet bool) {
 	logln := func(v ...interface{}) {
 		if !quiet {
 			log.Println(v...)
@@ -118,7 +124,7 @@ func handleClient(p1 io.ReadWriteCloser, p2 net.Conn, quiet bool) {
 	streamCopy := func(dst io.Writer, src io.ReadCloser) chan struct{} {
 		die := make(chan struct{})
 		go func() {
-			if _, err := generic.Copy(dst, src); err != nil {
+			if _, err := generic.Copy(dst, src, ctrl); err != nil {
 				if s1, ok := p1.(generic.Stream); ok {
 					// verbose error handling
 					cause := err