diff --git a/protocol/json/client_notification.go b/protocol/json/client_notification.go
index 44c6679..d9628e2 100644
--- a/protocol/json/client_notification.go
+++ b/protocol/json/client_notification.go
@@ -2,8 +2,8 @@ package json
 
 import (
 	"encoding/json"
+	"fmt"
 
-	crp "git.loafle.net/commons/rpc-go/protocol"
 	cuej "git.loafle.net/commons/util-go/encoding/json"
 )
 
@@ -21,7 +21,6 @@ type clientNotification struct {
 // ClientNotificationCodec decodes and encodes a single notification.
 type ClientNotificationCodec struct {
 	noti *clientNotification
-	err  error
 }
 
 func (cnc *ClientNotificationCodec) HasResponse() bool {
@@ -33,36 +32,26 @@ func (cnc *ClientNotificationCodec) Method() string {
 }
 
 func (cnc *ClientNotificationCodec) ReadParams(args []interface{}) error {
-	if cnc.err == nil && cnc.noti.Params != nil {
+	if nil != cnc.noti.Params {
 		// Note: if scr.request.Params is nil it's not an error, it's an optional member.
 		// JSON params structured object. Unmarshal to the args object.
 		if err := cuej.SetValueWithJSONStringArray(*cnc.noti.Params, args); nil != err {
-			cnc.err = &crp.Error{
-				Code:    crp.E_INVALID_REQ,
-				Message: err.Error(),
-				Data:    cnc.noti.Params,
-			}
-			return cnc.err
+			return err
 		}
 		return nil
 	}
-	return cnc.err
+	return fmt.Errorf("There is not params")
 }
 
 func (cnc *ClientNotificationCodec) Params() ([]string, error) {
-	if cnc.err == nil && cnc.noti.Params != nil {
+	if nil != cnc.noti.Params {
 		var values []string
 
 		if err := json.Unmarshal(*cnc.noti.Params, &values); err != nil {
-			cnc.err = &crp.Error{
-				Code:    crp.E_INVALID_REQ,
-				Message: err.Error(),
-				Data:    cnc.noti.Params,
-			}
-			return nil, cnc.err
+			return nil, err
 		}
 
 		return values, nil
 	}
-	return nil, cnc.err
+	return nil, fmt.Errorf("There is not params")
 }
diff --git a/protocol/json/client_response.go b/protocol/json/client_response.go
index 359f850..2b1559d 100644
--- a/protocol/json/client_response.go
+++ b/protocol/json/client_response.go
@@ -14,14 +14,13 @@ import (
 type clientResponse struct {
 	Version string           `json:"jsonrpc"`
 	Result  *json.RawMessage `json:"result,omitempty"`
-	Error   *json.RawMessage `json:"error,omitempty"`
+	Error   *protocol.Error  `json:"error,omitempty"`
 	ID      interface{}      `json:"id,omitempty"`
 }
 
 // ClientResponseCodec decodes and encodes a single request.
 type ClientResponseCodec struct {
 	res *clientResponse
-	err error
 }
 
 func (crc *ClientResponseCodec) ID() interface{} {
@@ -29,38 +28,22 @@ func (crc *ClientResponseCodec) ID() interface{} {
 }
 
 func (crc *ClientResponseCodec) Result(result interface{}) error {
-	if nil == crc.err && nil != crc.res.Result {
+	if nil == crc.res.Error && nil != crc.res.Result {
 		if err := json.Unmarshal(*crc.res.Result, result); nil != err {
-			crc.err = &protocol.Error{
-				Code:    protocol.E_PARSE,
-				Message: err.Error(),
-				Data:    crc.res.Result,
-			}
+			return err
 		}
 	}
 
-	return crc.err
+	return fmt.Errorf("There is no result")
 }
 
 func (crc *ClientResponseCodec) Error() *protocol.Error {
-	if nil == crc.res.Error {
-		return nil
-	}
-	protocolError := &protocol.Error{}
-	err := json.Unmarshal(*crc.res.Error, protocolError)
-	if nil != err {
-		return &protocol.Error{
-			Code:    protocol.E_PARSE,
-			Message: err.Error(),
-			Data:    crc.res.Error,
-		}
-	}
-	return protocolError
+	return crc.res.Error
 }
 
 func (crc *ClientResponseCodec) Notification() (protocol.ClientNotificationCodec, error) {
 	if nil != crc.res.ID || nil == crc.res.Result {
-		return nil, fmt.Errorf("RPC[JSON]: This is not notification")
+		return nil, fmt.Errorf("This is not notification")
 	}
 
 	noti := &clientNotification{}
@@ -69,7 +52,7 @@ func (crc *ClientResponseCodec) Notification() (protocol.ClientNotificationCodec
 		return nil, err
 	}
 
-	return &ClientNotificationCodec{noti: noti, err: err}, nil
+	return &ClientNotificationCodec{noti: noti}, nil
 }
 
 // newClientMessageCodec returns a new ClientMessageCodec.
@@ -79,19 +62,11 @@ func newClientResponseCodec(buf []byte) (protocol.ClientResponseCodec, error) {
 	err := json.Unmarshal(buf, res)
 
 	if err != nil {
-		err = &protocol.Error{
-			Code:    protocol.E_PARSE,
-			Message: err.Error(),
-			Data:    res,
-		}
+		return nil, fmt.Errorf("Cannot unmarshal response [%s] err: %v", string(buf), err)
 	}
 	if res.Version != Version {
-		err = &protocol.Error{
-			Code:    protocol.E_INVALID_REQ,
-			Message: "jsonrpc must be " + Version,
-			Data:    res,
-		}
+		return nil, fmt.Errorf("The protocol version of response[%s] is not %s", string(buf), Version)
 	}
 
-	return &ClientResponseCodec{res: res, err: err}, nil
+	return &ClientResponseCodec{res: res}, nil
 }
diff --git a/protocol/json/server_request.go b/protocol/json/server_request.go
index 2b9d214..a76a769 100644
--- a/protocol/json/server_request.go
+++ b/protocol/json/server_request.go
@@ -93,7 +93,7 @@ func (src *ServerRequestCodec) ReadParams(args []interface{}) error {
 		// JSON params structured object. Unmarshal to the args object.
 		if err := cuej.SetValueWithJSONStringArray(*src.req.Params, args); nil != err {
 			src.err = &protocol.Error{
-				Code:    protocol.E_INVALID_REQ,
+				Code:    protocol.E_BAD_PARAMS,
 				Message: err.Error(),
 				Data:    src.req.Params,
 			}
@@ -110,7 +110,7 @@ func (src *ServerRequestCodec) Params() ([]string, error) {
 
 		if err := json.Unmarshal(*src.req.Params, &values); err != nil {
 			src.err = &protocol.Error{
-				Code:    protocol.E_INVALID_REQ,
+				Code:    protocol.E_BAD_PARAMS,
 				Message: err.Error(),
 				Data:    src.req.Params,
 			}
@@ -122,21 +122,23 @@ func (src *ServerRequestCodec) Params() ([]string, error) {
 	return nil, src.err
 }
 
-func (src *ServerRequestCodec) NewResponse(reply interface{}) ([]byte, error) {
+func (src *ServerRequestCodec) NewResponse(reply interface{}, err error) ([]byte, error) {
 	res := &serverResponse{Version: Version, Result: reply, ID: src.req.ID}
-	return src.newServerResponse(res)
-}
-func (src *ServerRequestCodec) NewError(status int, err error) ([]byte, error) {
-	jsonErr, ok := err.(*protocol.Error)
-	if !ok {
-		jsonErr = &protocol.Error{
-			Code:    protocol.E_SERVER,
-			Message: err.Error(),
+
+	if nil != err {
+		jsonErr, ok := err.(*protocol.Error)
+		if !ok {
+			jsonErr = &protocol.Error{
+				Code:    protocol.E_SERVER,
+				Message: err.Error(),
+			}
 		}
+		res.Error = jsonErr
 	}
-	res := &serverResponse{Version: Version, Error: jsonErr, ID: src.req.ID}
+
 	return src.newServerResponse(res)
 }
+
 func (src *ServerRequestCodec) newServerResponse(res *serverResponse) ([]byte, error) {
 
 	return json.Marshal(res)
diff --git a/protocol/server_codec.go b/protocol/server_codec.go
index 2181669..e175973 100644
--- a/protocol/server_codec.go
+++ b/protocol/server_codec.go
@@ -11,6 +11,5 @@ type ServerCodec interface {
 type ServerRequestCodec interface {
 	RegistryCodec
 
-	NewResponse(reply interface{}) ([]byte, error)
-	NewError(status int, err error) ([]byte, error)
+	NewResponse(reply interface{}, err error) ([]byte, error)
 }
diff --git a/registry/rpc_registry.go b/registry/rpc_registry.go
index 8a158c9..4c4595f 100644
--- a/registry/rpc_registry.go
+++ b/registry/rpc_registry.go
@@ -65,7 +65,7 @@ func (rr *rpcRegistry) HasMethod(method string) bool {
 // excluding the charset definition.
 func (rr *rpcRegistry) Invoke(codec protocol.RegistryCodec) (result interface{}, err error) {
 	serviceSpec, methodSpec, errGet := rr.services.get(codec.Method())
-	if errGet != nil {
+	if nil != errGet {
 		return nil, errGet
 	}
 	// Decode the args.