Used oneof in blimp_message.proto

blimp/common/proto/protocol_control.proto

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package blimp;
 
 // Indicates the message-Id that the peer has most-recently processed.
 message CheckpointAckMessage {
   optional int64 checkpoint_id = 1;
 }
 
 // Contains Client->Engine information to establish an authenticated connection.
 message StartConnectionMessage {
   optional string client_token = 1;
   optional int32 protocol_version = 2;
 }
 
 message ProtocolControlMessage {
-  enum Type {
-    UNKNOWN = 0;
+  oneof connection_message {
+    // Client => Server types.
+    StartConnectionMessage start_connection = 41;
 
-    // Client => Server types.
-    START_CONNECTION = 1;
-
-    // Server => Client types will start from 100.
-
-    // Bi-directional types.
-    CHECKPOINT_ACK = 200;
+    // Server => Client types.
+    CheckpointAckMessage checkpoint_ack = 42;
   }
-
-  optional Type type = 1;
-
-  optional StartConnectionMessage start_connection = 1001;
-  optional CheckpointAckMessage checkpoint_ack = 1200;
 }