diff --git a/code/client/pool/send_vnc.go b/code/client/pool/send_vnc.go
index 8c676f2..0083f27 100644
--- a/code/client/pool/send_vnc.go
+++ b/code/client/pool/send_vnc.go
@@ -122,3 +122,16 @@ func (conn *Conn) SendVNCKeyboard(to string, toIdx uint32, id string,
 	case <-time.After(conn.parent.cfg.WriteTimeout):
 	}
 }
+
+// SendVNC send vnc keyboard event
+func (conn *Conn) SendVNCCADEvent(to string, toIdx uint32, id string) {
+	var msg network.Msg
+	msg.To = to
+	msg.ToIdx = toIdx
+	msg.XType = network.Msg_vnc_cad
+	msg.LinkId = id
+	select {
+	case conn.write <- &msg:
+	case <-time.After(conn.parent.cfg.WriteTimeout):
+	}
+}
diff --git a/code/client/tunnel/vnc/define/sas_windows.go b/code/client/tunnel/vnc/define/sas_windows.go
new file mode 100644
index 0000000..beb5a5f
--- /dev/null
+++ b/code/client/tunnel/vnc/define/sas_windows.go
@@ -0,0 +1,8 @@
+package define
+
+import "syscall"
+
+var (
+	libSas, _      = syscall.LoadLibrary("Sas.dll")
+	FuncSendSAS, _ = syscall.GetProcAddress(syscall.Handle(libSas), "SendSAS")
+)
diff --git a/code/client/tunnel/vnc/events.go b/code/client/tunnel/vnc/events.go
index f9cf029..d1898db 100644
--- a/code/client/tunnel/vnc/events.go
+++ b/code/client/tunnel/vnc/events.go
@@ -40,3 +40,7 @@ func (v *VNC) keyboardEvent(remote *pool.Conn, data []byte) {
 	remote.SendVNCKeyboard(v.link.target, v.link.targetIdx, v.link.id,
 		payload.Payload.Status, payload.Payload.Key)
 }
+
+func (v *VNC) cadEvent(remote *pool.Conn) {
+	remote.SendVNCCADEvent(v.link.target, v.link.targetIdx, v.link.id)
+}
diff --git a/code/client/tunnel/vnc/h_ws.go b/code/client/tunnel/vnc/h_ws.go
index 0476b13..05bf76f 100644
--- a/code/client/tunnel/vnc/h_ws.go
+++ b/code/client/tunnel/vnc/h_ws.go
@@ -103,6 +103,7 @@ func (v *VNC) localRead(ctx context.Context, local *websocket.Conn, remote *pool
 		case "keyboard":
 			v.keyboardEvent(remote, data)
 		case "cad":
+			v.cadEvent(remote)
 		}
 	}
 }
diff --git a/code/client/tunnel/vnc/link.go b/code/client/tunnel/vnc/link.go
index 80cf937..11af5c5 100644
--- a/code/client/tunnel/vnc/link.go
+++ b/code/client/tunnel/vnc/link.go
@@ -101,6 +101,8 @@ func (link *Link) remoteRead() {
 			link.ps.MouseEvent(msg.GetVmouse())
 		case network.Msg_vnc_keyboard:
 			link.ps.KeyboardEvent(msg.GetVkbd())
+		case network.Msg_vnc_cad:
+			link.ps.CADEvent()
 		case network.Msg_disconnect:
 			logging.Info("link %s disconnected", link.id)
 			return
diff --git a/code/client/tunnel/vnc/process/event_windows.go b/code/client/tunnel/vnc/process/event_windows.go
new file mode 100644
index 0000000..960bd45
--- /dev/null
+++ b/code/client/tunnel/vnc/process/event_windows.go
@@ -0,0 +1,15 @@
+package process
+
+import (
+	"natpass/code/client/tunnel/vnc/define"
+	"syscall"
+
+	"github.com/lwch/logging"
+)
+
+func (p *Process) CADEvent() {
+	ok, _, err := syscall.Syscall(define.FuncSendSAS, 1, 0, 0, 0)
+	if ok == 0 {
+		logging.Error("send sas failed: %v", err)
+	}
+}
diff --git a/html/vnc/index.js b/html/vnc/index.js
index f957783..696efed 100644
--- a/html/vnc/index.js
+++ b/html/vnc/index.js
@@ -64,7 +64,10 @@ var page = {
         });
     },
     cad: function() {
-        // TODO
+        if (!page.ws) {
+            return;
+        }
+        page.ws.send(JSON.stringify({action: 'cad'}));
     },
     mousemove: function(e) {
         if (!page.ws) {