How send arraybuffer as binary via Websocket?

Question

I am working on a project with Mozilla Europe. In this project, I use websocket by Worlize (server-side) and Mozilla (client side), Node.js to try to upload files from a client to a server.
My present goal is to send a arraybuffer of the file to the server. Create the arraybuffer and send it is fine.
But my server tells me that arraybuffer is a utf8 message and not a binary message.

Do I misunderstand something? If not, how can i correct that?

Client side:

    reader = new FileReader();
    reader.readAsArrayBuffer(file);
    reader.onload = function(e) {
        connection.send(e.target.result); 
    };

Server side:

ws.on('message', function(message,flags) {
if (!flags.binary) {
    //some code
}
else {
    console.log('It\'s a binary');
}

I try with Blob too, same result. The binary part is invisible.

This is a Q&A site, "fork and participate" isn't going to happen here (see http://stackoverflow.com/faq). Also, please don't ask people to dig through your code - include the minimal code necessary to explain what exactly you are doing. — Wladimir Palant, Mar 03 '12 at 20:46
I realise this was asked some time ago so having said that I just want to add that Firefox 11 and onwards support binary ArrayBuffer and Blob. — SpliFF, Jul 05 '12 at 01:35

score 29 · Answer 1 · edited Aug 08 '19 at 18:02

Gecko11.0 ArrayBuffer send and receive support for binary data has been implemented.

connection = new WebSocket( 'ws://localhost:1740' );
connection.binaryType = "arraybuffer";
connection.onopen = onopen;
connection.onmessage = onmessage;
connection.onclose = onclose;
connection.onerror = onerror;

sending Binary data:

function sendphoto() {
    imagedata = context.getImageData( 0, 0, imagewidth, imageheight );
    var canvaspixelarray = imagedata.data;
    var canvaspixellen = canvaspixelarray.length;
    var bytearray = new Uint8Array( canvaspixellen );
    for ( var i = 0; i < canvaspixellen; ++i ) {
        bytearray[i] = canvaspixelarray[i];
    }
    connection.send( bytearray.buffer );
    context.fillStyle = '#ffffff';
    context.fillRect( 0, 0, imagewidth, imageheight );
}

Recieving Binary Data:

if ( event.data instanceof ArrayBuffer ) {
    var bytearray = new Uint8Array( event.data );
    var tempcanvas = document.createElement( 'canvas' );
    tempcanvas.height = imageheight;
    tempcanvas.width = imagewidth;
    var tempcontext = tempcanvas.getContext( '2d' );
    var imgdata = tempcontext.getImageData( 0, 0, imagewidth, imageheight );
    var imgdatalen = imgdata.data.length;
    for ( var i = 8; i < imgdatalen; i++ ) {
        imgdata.data[i] = bytearray[i];
    }
    tempcontext.putImageData( imgdata, 0, 0 );
    var img = document.createElement( 'img' );
    img.height = imageheight;
    img.width = imagewidth;
    img.src = tempcanvas.toDataURL();
    chatdiv.appendChild( img );
    chatdiv.innerHTML = chatdiv.innerHTML + "<br />";
}

but how can I also send, say, the name of the flie along with the data? If I put it in a JSON, JSON.stringify doesn't work for arraybuffers... — B''H Bi'ezras -- Boruch Hashem, Feb 22 '19 at 06:42
@bluejayke Convert the string data into a typed array and combine the buffers. Also add a byte length flag to indicate the length of the file name buffer so the receiver knows how many bytes to read and send the combined buffer like: file name length|file name|the rest of the original data. — Matt, Apr 01 '20 at 23:56

score 1 · Answer 2 · edited Jul 05 '15 at 16:44

1

Note: Prior to version 11, Firefox only supported sending data as a string.

Source: https://developer.mozilla.org/en/WebSockets/Writing_WebSocket_client_applications

edited Jul 05 '15 at 16:44

scape

652
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answered Apr 05 '12 at 17:12

Dennis

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How send arraybuffer as binary via Websocket?

2 Answers2

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