sending a javascript object through websockets with faye

Question

Hi all I'm trying to send a javascript object through websockets:

the faye-websockets documentation says:

send(message) accepts either a String or a Buffer and sends a text or binary message over the connection to the other peer.

server side I'm using node and faye.

var WebSocket = require('faye-websocket');
var http = require('http');

var server = http.createServer();
server.addListener('upgrade', function(request, socket, head) {
    var ws = new WebSocket(request, socket, head);
    ws.send({topic:'handshake', data:'sdf487rgiuh7'});
});
server.listen(8000);

client side:

<script>
    var ws = new WebSocket('ws://localhost:8000');
    ws.onmessage = function(e) {
        console.log(e.data); //prints [Object object] string and not the object
    };
</script>

what is my error? Thanks

The -1 is likely due to the fact that the error message has already told you exactly what is wrong. — user663031
– user663031, Commented May 18, 2015 at 4:47

kanaka · Accepted Answer · 2012-10-23 15:39:31Z

106

WebSockets support sending and receiving: strings, typed arrays (ArrayBuffer) and Blobs. Javascript objects must be serialized to one of the above types before sending.

To send an object as a string you can use the builtin JSON support:

ws.send(JSON.stringify(object));

To send an object as a typed array you can use a javascript BSON library such as this one:

ws.send(BSON.serialize(object));

When you receive a WebSocket message you will need to deserialize it.

To deserialize a JSON string from a WebSocket message:

ws.onmessage = function (e) {
    var object = JSON.parse(e.data);
    ...
};

If you are using binary messages over WebSocket, then first you should set the binaryType attribute in order to receive all binary messages as typed arrays:

ws.binaryType = "arraybuffer";

Then the deserialization will look like this:

ws.onmessage = function (e) {
    var object = BSON.deserialize(e.data);
    ...
};

Here is a blog post about using BSON in Javascript;

answered Oct 23, 2012 at 15:39

kanaka

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4 Comments

Vadorequest Over a year ago

Your link is dead :/ And there aren't any readme.md on the git repo of js-bson. Gonna search some doc.

Martin Konecny Over a year ago

Is it possible that the onmessage callback doesn't return the entire json string, and therefore JSON.parse throws a parsing error?

kanaka Over a year ago

@MartinKonecny WebSockets is message based and messages are delivered in full (no partial messages). However, note that if you have something like websockify in the middle and you're actually talking to a regular TCP server on the other end, the message divisions are arbitrary (depend on TCP packet size, kernel window sizes, buffer sizes, etc). In that case you need to do some kind of re-assembly yourself.

Martin Konecny Over a year ago

Thanks, I thought websockets were just plain sockets initiated via http. Good to know to is message based.

Alex Ivasyuv · Accepted Answer · 2018-01-09 12:29:56Z

3

Client:

const bson = new BSON();
ws.binaryType = 'arraybuffer';

ws.onmessage = function(event) {
  console.log(bson.deserialize(Buffer.from(event.data)));
}

Server:

 const data = bson.serialize({ ... });
 ws.send(data);

answered Jan 9, 2018 at 12:29

Alex Ivasyuv

8,87418 gold badges77 silver badges91 bronze badges

Comments

Fabiel León · Accepted Answer · 2023-01-12 23:37:59Z

3

add a function called json to the websocket object that transform in json and send the object passed by parameter

ws.json = (obj) => ws.send(JSON.stringify(obj));

ws.json({ message: "hello" });

edited Jan 12, 2023 at 23:37

answered Oct 23, 2022 at 22:54

Fabiel León

1511 silver badge5 bronze badges

1 Comment

nima Over a year ago

While this code may answer the question, providing additional context regarding how and/or why it solves the problem would improve the answer's long-term value. You can find more information on how to write good answers in the help center: stackoverflow.com/help/how-to-answer . Good luck

udidu · Accepted Answer · 2012-10-23 11:00:49Z

2

I'm basically working with Socket.IO, but it looks like you need to stringify your data in the server and parse it in the client like so:

in the server:

ws.send(JSON.stringify({topic:'handshake', data:'sdf487rgiuh7'}));

in the client:

console.log(JSON.parse(e.data));

answered Oct 23, 2012 at 11:00

udidu

8,6167 gold badges53 silver badges69 bronze badges

4 Comments

frx08 Over a year ago

in your case you are sending a string but since faye supports sending binary data I want to exploit this feature

dom Over a year ago

@frx08 An JS object is no binary data, an image would be. So udidus answer is correct.

frx08 Over a year ago

so the only method to serialize a js object is to stringify it?

Michelle Tilley Over a year ago

"Stringifying" an object is another way to say "serialize with JSON"

Jayesh Maheshwari · Accepted Answer · 2023-06-12 05:52:10Z

0

From the client side you can just send it via JSON.strigify and in the server side just do JSON.parse to get the data

answered Jun 12, 2023 at 5:52

Jayesh Maheshwari

11 bronze badge

1 Comment

J4GD33P 51NGH Over a year ago

Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.

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