Question

It seems I don’t understand something simple about Protocol Buffers, but this is very important question for me and for my real use-case.

While reading documentation about Protocol Buffers I don’t understand how one know which message you should decode from the stream? All examples about some defined Message, but if you have defined several completelly different messages and you want to send those messages between 2 processes — how do you know which message you have just received?

Or maybe Protocol Buffers do not try to address this problem and leave this question for another abstraction level?

Or maybe I should pack the message into structure like that:

message wrapper {
   required string message_name = 1;
   string packed_message = 2; 
}

And then I should decode message in 2 stages: get the message_name at first, and then decode real packed message at second stage, should not I?

Answer 1

Look at self describing messages section