chelo_c chelo_c - 12 days ago 11
Java Question

How to send binary data with socket.io?

so I have been having real trouble sending binary data with socket.io in node.js (Js client and Android client).

There is not much information neither in:

http://socket.io/blog/introducing-socket-io-1-0/

http://socket.io/get-started/chat/

I need to use socket io to send a binary array, that I create and fill.

the only code they give is the following:

var socket = new WebSocket('ws://localhost');
socket.binaryType = 'arraybuffer';
socket.send(new ArrayBuffer);


My answer is bellow.

Answer

Finally I have it working with JS and Android ( Java ), so I decided to share it with you guys.

Let's start with the Server Code: (Node js)

var http = require('http');

var app = http.createServer(function ejecute(request, response){});
var io = require('socket.io').listen(app);


io.on('connection', function(socket) {
        socket.on('message', function(data){
            console.log("recieved data:");
            console.log(data);

            var bufArr = new ArrayBuffer(4);
            var bufView = new Uint8Array(bufArr);
            bufView[0]=6;
            bufView[1]=7;
            bufView[2]=8;
            bufView[3]=9;
            socket.emit('message',bufArr);
        });
    });
app.listen(3000);

Lets jump on to the Javascript client

  var socket = io("http://localhost:3000");
  socket.emit('message', 'hola from js client');

  socket.on('message', function(msg){
    var bufView = new Uint8Array(msg);
    console.log(msg)
  });

And finally, let's show the Android (java) client:

    final Socket socket = IO.socket("http://localhost:3000",opts);

    socket.on(Socket.EVENT_CONNECT, new Emitter.Listener() {
        @Override
        public void call(Object... args) {
            socket.emit("message","hello from java");
        }
    });


    socket.on("message", new Emitter.Listener() {

        @Override
        public void call(Object... args) {
            byte[] bytearray = (byte[])args[0]; //received bytes

            for  (byte b : bytearray) {
                System.out.println("byte"+b);
            }
        }

    });

   socket.on(Socket.EVENT_DISCONNECT, new Emitter.Listener() {
    @Override
    public void call(Object... args) {}
});

I hope it is useful to you all. Cheers!

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