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I'm making a java NIO server which receive messages, each message have its size on the head of the message, that why I'm reading first into a buffer which have default size(44), then get the complete size from this buffer, and then create a new buffer which is supposed to get the rest of the message(body) and then use System.arrayCopy() to make an array with the complete message. this operations are working good, the problem is that the second buffer(body of the message)have the size but does not contain the right data. plz here is my code if you something wrong :

public void getMessageByMessageSize(SelectionKey key) {
    socket = (SocketChannel) key.channel();
    int nBytes = 0;
    byte[] message = null;
    try {
        nBytes = socket.read(headBuffer);
        if (nBytes < 0) {
            try {
                key.channel().close();
                key.cancel();
                return;
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
                    //size of the message body
        int corpMessageSize = MessageUtils.getMessageSize(headBuffer)
                - HEADER_SIZE;
        ByteBuffer corpsBuffer = ByteBuffer.allocate(corpMessageSize);
        headBuffer.flip();
        nBytes += socket.read(corpsBuffer);
        corpsBuffer.flip();
        byte[] corp=corpsBuffer.array();

        message = new byte[nBytes];
        System.arraycopy(headBuffer.array(), 0, message, 0, HEADER_SIZE);
        System.arraycopy(corpsBuffer.array(), 0, message, HEADER_SIZE,
                nBytes - HEADER_SIZE);
        System.out.println(nBytes);
        headBuffer.clear();
        corpsBuffer.clear();
    } catch (IOException e) {
        e.printStackTrace();
        try {
            key.channel().close();
            key.cancel();
            return;
        } catch (IOException ex) {
            e.printStackTrace();
        }
    }

    this.worker.verifyConnection(this,message, key);
    //this.worker.processData(this, socket, message, nBytes);
}

i have a simple client which send create a byte message, make its size in the head, and then send it.

thanks

Fozix
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1 Answers1

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nBytes += socket.read(corpsBuffer);

You are assuming that this reads the entire message and fills the buffer. Nothing in TCP/IP guarantees that. You have to loop. If you're in non-blocking mode, you have to re-select if you get a zero length read.

user207421
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  • with the client i send a message of 50 bytes, header of 44 bytes and 6 bytes of data bytes, in the server i read the header first "nBytes" is equal to 44, and then extract the size from the header and allocate "TOTAL_SIZE - HEADER_SIZE" to the "corpsBuffer" The nBytes += socket.read(corpsBuffer); read 6 bytes (size of data) and "nBytes" is equal to 50, the data( 6 bytes) i set them to 0xff all , and from nBytes += socket.read(corpsBuffer); i get 4 bytes of 0xff and the two last bytes are 0x00. i don't think that i have to loop again, but i will try it because i'm realy blocked, thanks EJP – Fozix Jul 13 '12 at 07:09
  • i think i get the last 4 bytes, and the two bytes just after the header are lost, any idea! – Fozix Jul 13 '12 at 07:20
  • @Fozix I can't follow all that, but it's simple. Either you got the entire request body or you didn't. If you didn't, you have to loop, and you have to *check* the result of `read()` in order to know whether you did or you didn't. – user207421 Jul 13 '12 at 10:22