diff --git a/msg.pb.go b/msg.pb.go
index 74c25ea..69338f5 100644
--- a/msg.pb.go
+++ b/msg.pb.go
@@ -20,6 +20,34 @@ var _ = math.Inf
 // proto package needs to be updated.
 const _ = proto.ProtoPackageIsVersion3 // please upgrade the proto package
 
+type MyMsg_TYPE int32
+
+const (
+	MyMsg_DATA  MyMsg_TYPE = 0
+	MyMsg_PING  MyMsg_TYPE = 1
+	MyMsg_CATCH MyMsg_TYPE = 2
+)
+
+var MyMsg_TYPE_name = map[int32]string{
+	0: "DATA",
+	1: "PING",
+	2: "CATCH",
+}
+
+var MyMsg_TYPE_value = map[string]int32{
+	"DATA":  0,
+	"PING":  1,
+	"CATCH": 2,
+}
+
+func (x MyMsg_TYPE) String() string {
+	return proto.EnumName(MyMsg_TYPE_name, int32(x))
+}
+
+func (MyMsg_TYPE) EnumDescriptor() ([]byte, []int) {
+	return fileDescriptor_c06e4cca6c2cc899, []int{0, 0}
+}
+
 type MyMsg struct {
 	Id                   string   `protobuf:"bytes,1,opt,name=id,proto3" json:"id,omitempty"`
 	Type                 int32    `protobuf:"varint,2,opt,name=type,proto3" json:"type,omitempty"`
@@ -219,6 +247,7 @@ func (m *Frame) GetDataid() []int32 {
 }
 
 func init() {
+	proto.RegisterEnum("MyMsg_TYPE", MyMsg_TYPE_name, MyMsg_TYPE_value)
 	proto.RegisterType((*MyMsg)(nil), "MyMsg")
 	proto.RegisterType((*Frame)(nil), "Frame")
 }
@@ -226,24 +255,27 @@ func init() {
 func init() { proto.RegisterFile("msg.proto", fileDescriptor_c06e4cca6c2cc899) }
 
 var fileDescriptor_c06e4cca6c2cc899 = []byte{
-	// 302 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x54, 0x91, 0xcd, 0x4e, 0x02, 0x31,
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-	0x2f, 0xec, 0x5a, 0x43, 0x79, 0x95, 0x4d, 0x85, 0xe4, 0x19, 0x6f, 0xa1, 0x0c, 0xca, 0xd7, 0x26,
-	0x50, 0xc1, 0xbd, 0xa4, 0x62, 0x57, 0xab, 0xa0, 0xa8, 0x57, 0x65, 0xd3, 0x91, 0xe4, 0x39, 0x76,
-	0x3d, 0xff, 0x41, 0x82, 0x37, 0x24, 0x85, 0xd7, 0x20, 0x56, 0x2a, 0xac, 0xde, 0xa9, 0x64, 0x7b,
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-	0xa3, 0x0d, 0x0d, 0xd8, 0x3d, 0x48, 0x7c, 0x00, 0x4c, 0xe3, 0x62, 0xb9, 0x5d, 0xaf, 0x8d, 0xef,
-	0xec, 0x8f, 0xa1, 0x21, 0x97, 0x2e, 0x53, 0x32, 0x3b, 0x06, 0x78, 0x0f, 0xe3, 0x43, 0xdd, 0xa9,
-	0xef, 0x2f, 0xdb, 0x10, 0x70, 0xf5, 0x3c, 0xb9, 0x73, 0x36, 0xf1, 0x09, 0x6e, 0x0e, 0x35, 0x6f,
-	0x3a, 0xd3, 0xe8, 0x45, 0xb0, 0xce, 0xb8, 0x8e, 0xce, 0xb8, 0x7d, 0x95, 0x42, 0xc9, 0xd9, 0x2b,
-	0x47, 0x93, 0xdf, 0x0c, 0xc4, 0x8b, 0x57, 0xce, 0x1c, 0x69, 0x65, 0xa7, 0xb4, 0xf6, 0x9b, 0x98,
-	0xe1, 0x40, 0x26, 0x85, 0x77, 0x30, 0x88, 0x6f, 0x5c, 0xcf, 0x1c, 0x0b, 0x79, 0xd4, 0xe9, 0x0a,
-	0x3d, 0xde, 0x92, 0xae, 0xc0, 0x64, 0xc5, 0x29, 0xd9, 0xf8, 0x5a, 0x4d, 0x65, 0x55, 0x44, 0xb2,
-	0x7b, 0x35, 0x1b, 0xbd, 0x41, 0x6b, 0x9b, 0x3a, 0x6c, 0x9b, 0xc6, 0x7c, 0x2e, 0x4b, 0xc6, 0xfd,
-	0xfc, 0x1f, 0x00, 0x00, 0xff, 0xff, 0x8f, 0x2a, 0xd3, 0xc5, 0xed, 0x01, 0x00, 0x00,
+	// 339 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x54, 0x51, 0xcb, 0x6e, 0xe2, 0x30,
+	0x14, 0x1d, 0x27, 0x71, 0x48, 0xee, 0x30, 0x28, 0x73, 0x67, 0x5a, 0x59, 0x5d, 0x45, 0x48, 0x48,
+	0x6c, 0xda, 0x45, 0xfb, 0x05, 0x40, 0x9f, 0x0b, 0x2a, 0x14, 0x65, 0xd3, 0x6e, 0x50, 0x20, 0x26,
+	0xb5, 0xda, 0x84, 0x28, 0x31, 0x6a, 0xe9, 0x2f, 0xf4, 0x2f, 0xfb, 0x25, 0x95, 0x2f, 0x06, 0x89,
+	0x95, 0xcf, 0x4b, 0xb6, 0x75, 0x0e, 0x84, 0x65, 0x5b, 0x5c, 0xd4, 0xcd, 0x5a, 0xaf, 0xfb, 0xdf,
+	0x0e, 0xf0, 0xe9, 0x76, 0xda, 0x16, 0xd8, 0x03, 0x47, 0xe5, 0x82, 0xc5, 0x6c, 0x18, 0x26, 0x8e,
+	0xca, 0x11, 0xc1, 0xd3, 0xdb, 0x5a, 0x0a, 0x27, 0x66, 0x43, 0x9e, 0x10, 0xc6, 0x53, 0xf0, 0x75,
+	0xd6, 0x14, 0x52, 0x0b, 0x97, 0x72, 0x96, 0x99, 0x6c, 0x9e, 0xe9, 0x4c, 0x78, 0x31, 0x1b, 0x76,
+	0x13, 0xc2, 0x26, 0xdb, 0xd0, 0x1b, 0x82, 0xd3, 0x0d, 0x96, 0xe1, 0x7f, 0xe0, 0xcb, 0x4c, 0x2f,
+	0x5f, 0x84, 0x4f, 0xf2, 0x8e, 0x60, 0x04, 0xee, 0xab, 0xdc, 0x8a, 0x0e, 0x69, 0x06, 0xa2, 0x80,
+	0x8e, 0x5e, 0xd6, 0xe5, 0x3a, 0x97, 0x22, 0x20, 0x75, 0x4f, 0xf1, 0x1c, 0xd0, 0xc2, 0xf9, 0x62,
+	0xb3, 0x5a, 0xc9, 0xa6, 0x55, 0x9f, 0x52, 0x84, 0x14, 0xfa, 0x6b, 0x9d, 0xf1, 0xc1, 0xc0, 0x01,
+	0xf4, 0xf6, 0xf1, 0x32, 0xfb, 0x78, 0x57, 0x95, 0x00, 0x8a, 0xfe, 0xb1, 0xea, 0x94, 0x44, 0xbc,
+	0x84, 0x93, 0x7d, 0xac, 0x91, 0xad, 0xac, 0xf2, 0xb9, 0x56, 0xa5, 0x2c, 0x5b, 0xf1, 0x9b, 0xd2,
+	0xff, 0xac, 0x99, 0x90, 0x97, 0x92, 0xd5, 0x1f, 0x80, 0x97, 0x3e, 0xcd, 0x6e, 0x30, 0x00, 0xef,
+	0x7a, 0x94, 0x8e, 0xa2, 0x5f, 0x06, 0xcd, 0x1e, 0x1e, 0xef, 0x22, 0x86, 0x21, 0xf0, 0xc9, 0x28,
+	0x9d, 0xdc, 0x47, 0x4e, 0xff, 0x8b, 0x01, 0xbf, 0x6d, 0xb2, 0x52, 0x1e, 0x4a, 0x65, 0xc7, 0xa5,
+	0xee, 0x1e, 0xa4, 0xaa, 0x83, 0xc4, 0x32, 0x3c, 0x83, 0xc0, 0x9c, 0xe6, 0x17, 0x54, 0xb7, 0x9b,
+	0x1c, 0xb8, 0x1d, 0xcb, 0xa3, 0x5b, 0xec, 0x58, 0x34, 0x00, 0x3f, 0x1e, 0xc0, 0x9c, 0x2a, 0x17,
+	0x7e, 0xec, 0x9a, 0x01, 0x76, 0x6c, 0xdc, 0x7d, 0x86, 0x5a, 0x55, 0x85, 0xde, 0x54, 0x95, 0x7c,
+	0x5b, 0xf8, 0xb4, 0xca, 0xd5, 0x4f, 0x00, 0x00, 0x00, 0xff, 0xff, 0xb6, 0x1b, 0xbb, 0x28, 0x14,
+	0x02, 0x00, 0x00,
 }
diff --git a/msg.proto b/msg.proto
index d13a95f..7c8086b 100644
--- a/msg.proto
+++ b/msg.proto
@@ -1,6 +1,12 @@
 syntax = "proto3";
 option go_package = "pingtunnel";
 message MyMsg {
+  enum TYPE {
+    DATA = 0;
+    PING = 1;
+    CATCH = 2;
+  }
+
   string id = 1;
   int32 type = 2;
   string target = 3;
diff --git a/pingtunnel.go b/pingtunnel.go
index f2a1884..13ccd9e 100644
--- a/pingtunnel.go
+++ b/pingtunnel.go
@@ -19,7 +19,6 @@ const (
 	DATA  uint32 = 0x01010101
 	PING  uint32 = 0x02020202
 	CATCH uint32 = 0x03030303
-	END   uint32 = 0xAAAABBBB
 )
 
 type MyMsg struct {