diff --git a/client/client_sniffer.go b/client/client_sniffer.go
index 8dbba44..b4a5900 100644
--- a/client/client_sniffer.go
+++ b/client/client_sniffer.go
@@ -81,6 +81,7 @@ func checkPacket(packet gopacket.Packet) {
 //todo： udp connection can be reused.
 func call(msg []byte) {
 
+	//fixme when quickly send 2 packets it goes wrong!
 	lAddr := &net.UDPAddr{IP: net.ParseIP("localhost"), Port: constant.MapSendPort}
 	rAddr := &net.UDPAddr{IP: net.ParseIP(constant.ServerIp), Port: utils.GetMapPort()}
 	conn, err := net.DialUDP("udp", lAddr, rAddr)
diff --git a/main/cohvs_main.go b/main/cohvs_main.go
index ad660e7..c04e316 100644
--- a/main/cohvs_main.go
+++ b/main/cohvs_main.go
@@ -22,7 +22,9 @@ func main() {
 	for _, arg := range os.Args {
 		if arg=="server"{
 			serverMode = true
-			break
+		}
+		if arg=="cson"{
+			server.SwitchOnCompatiSymmetric()
 		}
 		if arg=="mock"{
 			fmt.Println("start up as mock mode")
diff --git a/server/multi_server.go b/server/multi_server.go
index 03c9164..67b4b1d 100644
--- a/server/multi_server.go
+++ b/server/multi_server.go
@@ -46,6 +46,7 @@ func GetMultiServer() *MultiServer {
 func (server *MultiServer) Work() {
 
 	fmt.Println("Server start......")
+	fmt.Println("compatiSymmetric switch is ",compatiSymmetric)
 
 	server.controller.work()
 
diff --git a/server/v_player.go b/server/v_player.go
index 7ae55a8..8902904 100644
--- a/server/v_player.go
+++ b/server/v_player.go
@@ -64,13 +64,30 @@ func (p *VPlayer) handle(msg []byte, raddr *net.UDPAddr) {
 func (controller *VPlayerController) findUser(addr *net.UDPAddr) *VPlayer {
 	for i := range controller.players {
 		p := &controller.players[i]
-		if p.playerAddr != nil && p.playerAddr.String() == addr.String() {
+		if ipUserCheck(p.playerAddr,addr){
 			return p
 		}
 	}
 	return nil
 }
 
+func SwitchOnCompatiSymmetric(){
+	compatiSymmetric = true
+}
+
+var compatiSymmetric = false
+
+func ipUserCheck(local *net.UDPAddr,remote *net.UDPAddr) bool{
+	if local==nil{
+		return false
+	}
+	if compatiSymmetric{
+		return local.IP.String()==remote.IP.String()
+	}else{
+		return local.String()==remote.String()
+	}
+}
+
 func (controller *VPlayerController) register(addr *net.UDPAddr) string{
 	for i := range controller.players {
 		p := &controller.players[i]