Issue related to server side deserialization in protobufJS

[barbareek]

In my proto file i have int32 type message field, i encode the details and send it over to a java client where in i am decoding this value , values are being decode properly till 126 but beyond that i.e for a value of 127 corresponding decoded value is 253

[dcodeIO]

This is probably happening because the data is converted to a string somewhere on its way.

See: https://github.com/dcodeIO/ProtoBuf.js/wiki/How-to-read-binary-data-in-the-browser-or-under-node.js%3F

[barbareek]

well, I have now placed a nodejs server to decode the protobuf data sent from browser(sending 300 value).
In nodejs server i am able to get 300(correct value ) but when i send the same stream to java client where in i am using corresponding getter method to retrieve the value i am getting 381.

hex value sent from browser
08ac02200028003800

value recieved at nodejs server:
Buffer 08 ac 02 20 00 28 00 38 00

value decoded in java tcp client
381

[dcodeIO]

Could you put some code examples together for me that contain the following?

• The full process from encoding the message and sending it to a socket on the JavaScript side
• The full process from receiving the message and decoding it on the Java side

As all values up to 127 seem to work properly, I assume that there is some sort of string conversion in between (which is a common cause of such issues) that corrupts non-ASCII values (> 127). Hence the reference to the binary FAQ. It's mandatory to prevent unchecked string conversions to occur or, if not preventable, to use base64 encoding for example.

[barbareek]

var builder =  dcodeIO.ProtoBuf.loadJsonFile('json/test.json');
var package = builder.build("protocol");
var message = package.messageName;
var Message = new message(test);
// ajax request to server
$.ajax({
                                url: 'api/GPBSend',
                                type: 'POST',
                                data: {
                                    selectedType: 'Wrapper',
                                    jsonData: JSON.stringify(test),
                                    amg_serial:container.find('.amg_serial')[0].value,
                                    buffer:Wrapper.encodeHex()
                                },
                                success: function(data, textStatus, jqXHR) {
                                    Util.showMessage('UI_Container', "GPB Sent successfully", 'alert-success');
                                },
                                error: function(jqXHR, textStatus, errorThrown) {
                                    Util.showMessage('UI_Container', jqXHR.responseJSON.response, 'alert-danger');
                                }
                            });

// above request is processed by node.js

...
 queryObj = queryString.parse(body),
....
 buffer1 = queryObj.buffer;
var protoBufferSent = new Buffer(buffer1, 'hex'); // Is this the issue please suggest
.....
// sending request to tcp java client
// I am sending the length of protobuf as well 
  arrayOfBytes.push(getByteArray(protoBufferSent.length, 4));
  arrayOfBytes.push(protoBufferSent);
  console.log("connection established ......",Buffer.concat(arrayOfBytes));
  srvSocket.write(Buffer.concat(arrayOfBytes));
 srvSocket.end();

// In the java side 

//... get protobuf byte[] chunk(protobyte) from stream

Message v = Message.parseFrom(protobyte);
System.out.println("message id that had to be 300 "+v.getMessageId()); // but displayed as 381

[dcodeIO]

Well, this looks OK so far but, unfortunately, I have no simple solution for you. Looks like something else is going wrong and that the only way to figure this out for sure is to evaluate the contents of the actual byte arrays in between the several conversion steps. As node.js decodes it properly, I'd assume the cause is located somewhere near the Java side of things.

See: How to validate / decode / reverse engineer a protobuf buffer by hand?

[barbareek]

got it! I think best way to send data over tcp would be message.encode().toBuffer() now i am getting the values approproiately.