I am using javascript as client and a python as server.

I need to send/receive in between them using protocol buffer.

My proto looks like this :

message CMsgBase
{
    required CMsgHead msghead           = 1;
    optional bytes msgbody              = 2;
}

message CMsgHead
{
    required int32 msgtype                = 1;
    required int32 msgcode                = 2;
}

I am using protobuf.js in javascript and is sending the data to server using XMLHttpRequest with a POST method :

xhr.send(pbMessage.encodeAB());

The server side can receive this message and decode it successfully:

BaseHTTPServer

def do_POST(self):
    pbMessage = self.rfile.read(length) 
    # ...

The problem is that I can not decode the data in javascript side received from the server side.

Here is how I send the data to client from server :

pbMessageReturn = CMsgBase()
# ......
self.send_response(200)
self.end_headers()

"""Serializes the protocol message to a binary string.

Returns:
  A binary string representation of the message if all of the required
  fields in the message are set (i.e. the message is initialized).
"""

self.wfile.write(pbMessageReturn.SerializeToString())

And here is the result of print(pbMessageReturn) in server side :

msghead {
  msgtype: 10006
  msgcode: 1
}
msgbody: "\n\014192.168.1.16"

Everything seem s to be fine.

And here is how I decode the message from server in javascript:

xhr.onreadystatechange = function() {
    if (xhr.readyState == 4) {
        var result = xhr.responseText;
        var recvMessage = CMsgBase.decode(result, "utf8");
    }
};

And I am having an error:

protobuf.js:2335 Uncaught Error: Missing at least one required field for Message .CMsgBase: msghead(…)

BTW, if I try to send the back the data without serialize it:

self.wfile.write(pbMessageReturn)

The response I get in javascript is :

console.log(xhr.responseText);

msghead {
  msgtype: 10006
  msgcode: 1
}
msgbody: "\n\014192.168.1.16"

I am really not sure if the error is in the server side or the client side.

Any advice will be appreciated, thanks :)