Convert Java ByteBuffer to JavaScript ArrayBuffer

Question

I like to send a ArrayBuffer from JavaScript to an WebSocket Server, which Returns the Binary back to other Clients in the Network.

My Problem is, that I don't know how to send the ArrayBuffer from JavaScript 1:1 to the Server and from the Server back to the Client.

I tried a simple ByteBuffer, but it sends only one Array Element. Then I tried:

        InputStream arrayIO = new ByteArrayInputStream(payloadIO);
        ByteBuffer bufferIO = ByteBuffer.allocate(payloadIO.length + 1);

        while (arrayIO.available() > 0) {
            bufferIO.put((byte) arrayIO.read());
        }

        for (Session rowIO : sessionsIO.values()) {
            if (rowIO.isOpen()) {
                rowIO.getRemote().sendBytes(bufferIO);
            }
        }

Which gives me:

Buffer [0]
0: 0
offset: (...)
parent: (...)
buffer: (...)
byteLength: (...)
byteOffset: (...)
length: (...)
Symbol(Symbol.toStringTag): (...)
__proto__: Uint8Array

On the JavaScript Part.

anthumchris · Accepted Answer · 2021-03-04 23:09:23Z

1

You could convert the bytes to a string list and then parse them back into binary bytes.

class ArrayBufferUtil {
  static toString(buffer) {
    return new Uint8Array(buffer).toString()
  }
  
  static parse(s) {
    return new Uint8Array(
      s.split(',').map(i => parseInt(i, 10))
    ).buffer
  }
}

Test

console.log( ArrayBufferUtil.toString( new ArrayBuffer(8) ))
console.log( ArrayBufferUtil.parse( '0,0,0,0,0,0,0,0' ))

answered Mar 4, 2021 at 23:09

anthumchris

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Comments

Jan Heil · Accepted Answer · 2021-03-06 11:10:17Z

0

I fixed it by adding an offset on the Client receiving site. The Server sending an Opcode on the first 4 Bytes (RFC6455).

dataIO.buffer.slice(4)

answered Mar 6, 2021 at 11:10

Jan Heil

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