diff --git a/constants.go b/constants.go
index 154e985..a42c25e 100644
--- a/constants.go
+++ b/constants.go
@@ -1,17 +1,71 @@
 package overflow_gateway_websocket
 
 import (
+	"encoding/json"
+	"fmt"
+
 	cuc "git.loafle.net/commons_go/util/context"
 )
 
 var (
 	ServletSocketKey = cuc.ContextKey("ServletSocket")
+	ClientTypeKey    = cuc.ContextKey("ClientType")
 	SocketIDKey      = cuc.ContextKey("SocketID")
+	TargetIDKey      = cuc.ContextKey("TargetID")
 )
 
 const (
 	ConfigPathFlagName = "config-dir"
 	ConfigFileName     = "config.json"
 
-	GRPCSessionIDKey = "SESSION_ID"
+	GRPCClientTypeKey = "@@OVERFLOW::CLIENT_TYPE"
+	GRPCSessionIDKey  = "@@OVERFLOW::SESSION_ID"
+	GRPCTargetIDKey   = "@@OVERFLOW::TARGET_ID"
 )
+
+type ClientType int
+
+const (
+	MEMBER ClientType = iota
+	PROBE
+)
+
+var (
+	clientTypeID = map[ClientType]string{
+		MEMBER: "MEMBER",
+		PROBE:  "PROBE",
+	}
+
+	clientTypeName = map[string]ClientType{
+		"MEMBER": MEMBER,
+		"PROBE":  PROBE,
+	}
+)
+
+func (ct ClientType) String() string {
+	return clientTypeID[ct]
+}
+
+func (ct *ClientType) MarshalJSON() ([]byte, error) {
+	value, ok := clientTypeID[*ct]
+	if !ok {
+		return nil, fmt.Errorf("Invalid EnumType[%s] value", *ct)
+	}
+	return json.Marshal(value)
+}
+
+func (ct *ClientType) UnmarshalJSON(b []byte) error {
+	// unmarshal as string
+	var s string
+	err := json.Unmarshal(b, &s)
+	if err != nil {
+		return err
+	}
+
+	value, ok := clientTypeName[s]
+	if !ok {
+		return fmt.Errorf("Invalid EnumType[%s] value", s)
+	}
+	*ct = value
+	return nil
+}
diff --git a/internal/server/rpc/gateway_rpc_servlet_handlers.go b/internal/server/rpc/gateway_rpc_servlet_handlers.go
index 18e8c65..9f42e19 100644
--- a/internal/server/rpc/gateway_rpc_servlet_handlers.go
+++ b/internal/server/rpc/gateway_rpc_servlet_handlers.go
@@ -24,7 +24,10 @@ type GatewayRPCServletHandlers struct {
 }
 
 func (sh *GatewayRPCServletHandlers) Invoke(servletCTX rpc.ServletContext, requestCodec protocol.RegistryCodec) (result interface{}, err error) {
-	md := metadata.Pairs(oogw.GRPCSessionIDKey, servletCTX.GetAttribute(oogw.SocketIDKey).(string))
+	md := metadata.Pairs(
+		oogw.GRPCClientTypeKey, servletCTX.GetAttribute(oogw.SocketIDKey).(string),
+		oogw.GRPCSessionIDKey, servletCTX.GetAttribute(oogw.SocketIDKey).(string),
+		oogw.GRPCTargetIDKey, servletCTX.GetAttribute(oogw.SocketIDKey).(string))
 	grpcCTX := metadata.NewOutgoingContext(context.Background(), md)
 
 	params, err := requestCodec.Params()