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

Answer 1

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;

Answer 2

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);

Answer 3

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));