Use Chromium BUILD to approximate Blimp protocol version, and check it.

blimp/common/proto/protocol_control.proto

Index: blimp/common/proto/protocol_control.proto
diff --git a/blimp/common/proto/protocol_control.proto b/blimp/common/proto/protocol_control.proto
index 7dd1004490270137fa3ead2a340092cf8658cc8c..9ee84c2d3842a855e3825471b93a154b5e151239 100644
--- a/blimp/common/proto/protocol_control.proto
+++ b/blimp/common/proto/protocol_control.proto
@@ -19,6 +19,16 @@ message StartConnectionMessage {
   optional int32 protocol_version = 2;
 }
 
+// Indicates the reason for the peer ending the connection.
+message EndConnectionMessage {
+  enum Reason {
+    UNKNOWN = 0;
+    AUTHENTICATION_FAILED = 1;
+    PROTOCOL_MISMATCH = 2;
+  };
+  optional Reason reason = 1;
+}
+
 message ProtocolControlMessage {
   enum Type {
     UNKNOWN = 0;
@@ -30,10 +40,13 @@ message ProtocolControlMessage {
 
     // Bi-directional types.
     CHECKPOINT_ACK = 200;
+    END_CONNECTION = 201;

[Sriram, 2016/04/22 21:07:34]

Shouldn't this be Server -> Client type instead of bidirectional? i.e. in 100's
range instead of 201?

   }
 
   optional Type type = 1;
 
   optional StartConnectionMessage start_connection = 1001;
+
   optional CheckpointAckMessage checkpoint_ack = 1200;
+  optional EndConnectionMessage end_connection = 1201;
 }