C# websocket: how do I send binary data to a client?

Question

I am trying to send a image (.png) as a binary blob to a javascript client:

  static Byte[] imageResponse(string pngPath)
  {
        Byte[] image = System.IO.File.ReadAllBytes(pngPath);
        ulong n = (ulong) image.Length;
        byte[] data = new byte[n + 10];
        data[0] = 130; // binary ?
        data[1] = 127;
        Byte[] na = BitConverter.GetBytes(n); // correct endinaness?
        Array.Copy(na, 0, data, 2, 8);
        Array.Copy(image, 0, data, 10, (int) n);
        return data;
  }

 string path = "C:/tmp/crl3400.png";
 Byte[] bresponse = imageResponse(path);
 stream.Write(bresponse, 0, bresponse.Length);

However in the client I am not receiving any message:

var socket = new WebSocket( "ws://127.0.0.1:80" );
socket.binaryType = "arraybuffer"; // allow both text and binary data to be transfered.
socket.onopen = function ( event ) {
    alert( "WebSocket opened!" );
    socket.send( "Hello server!" );
};
socket.onmessage = function ( event ) {
    alert( "onmessage" );
    var arrayBufferView = new Uint16Array( event.data );
    var blob = new Blob( [arrayBufferView], { type: "image/png" } );
    var urlCreator = window.URL || window.webkitURL;
    var imageUrl = urlCreator.createObjectURL( blob );
    var img = document.querySelector( "#image" );
    img.src = imageUrl;
};
socket.onerror = function ( event ) {
    alert( "Error" );
}

What could be wrong? Things worked when I sent the text "Hello client!". I am not getting an Error alert. On the server I am receiving "Hello server!" fine.

Should it be Uint8Array and not Uint16?

TYY
– TYY

2015-11-18 15:17:09 +00:00
Commented Nov 18, 2015 at 15:17 — TYY
– TYY, Commented Nov 18, 2015 at 15:17

Lnn · Accepted Answer · 2017-01-11 04:11:06Z

1

The msg.data is type of Blob, so you just use urlCreator.createObjectURL(blob); method bla bla bla....

answered Jan 11, 2017 at 4:11

Lnn

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