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Thread: NIO UDP DatagramChannel data not sending outů

  1. #1
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    Default NIO UDP DatagramChannel data not sending outů

    Nice to meet you, dear all.

    I'm a beginner and this is my first time programming such thing using Java.

    I'm writing a program which gets data input from a port, saves it into a buffer, and when the buffer is full, it'll send out the data using another port. The protocol is UDP.

    So here is my code:

    try {
        // UDP data-in settings
        DatagramChannel inChannel = DatagramChannel.open();
        SocketAddress inAddress = new InetSocketAddress(FMBuffer.IN_PORT);
        inChannel.bind(inAddress);
     
        // UDP data-out settings
        DatagramChannel outChannel = DatagramChannel.open();
        SocketAddress outAddress = new InetSocketAddress(FMBuffer.OUT_PORT);
        outChannel.bind(outAddress);
     
        LinkedList<ByteBuffer> buffer = new LinkedList<ByteBuffer>();
        ByteBuffer b = ByteBuffer
                .allocateDirect(FMBuffer.UDP_MAX_PACKET_SIZE);
     
        while (true) {          
     
            if (inChannel.receive(b) != null) { // Receive data and put into b
                b.flip();                   
                // Save b into the buffer
                buffer.addLast(b);
     
                System.out.print("In(" + buffer.size() + "): ");
                while (buffer.getLast().hasRemaining()) {                           
                    System.out.write(buffer.getLast().get());
                }
                System.out.println();
     
                // If the buffer reaches the set limit
                if (buffer.size() > FMBuffer.BUFFER_LIST_SIZE) {
                    // Send the first b out, then remove it
                    System.out.print("Out(" + buffer.size() + "): ");
                    while (buffer.getFirst().hasRemaining()) {                          
                        System.out.write(buffer.getFirst().get());
                        outChannel.send(buffer.getFirst(), outAddress);
                    }
                    System.out.println();
                    buffer.removeFirst();
                }
     
                b.clear();
     
            } else { // Receive no data
                if (buffer.size() > 0) {
                    // Send the first b out, then remove it
                    System.out.print("Out remaining(" + buffer.size() + "): ");
                    while (buffer.getFirst().hasRemaining()) {                          
                        System.out.write(buffer.getFirst().get());
                        outChannel.send(buffer.getFirst(), outAddress);
                    }
                    System.out.println();
                    buffer.removeFirst();
                }
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

    There are several problems...

    I tried to use a program to read from 127.0.0.1:OUT_PORT. The program said that the port is in use. What shall I do?

    Say BUFFER_LIST_SIZE = 5 and outChannel.send(...) is commented. The output data is always blank, not the input one. Also, if I stop sending data to it, it will not output the remaining data from its buffer. With inputs like "* UDP Flood. Server stress test ****", it will output:

     
        In(1): ***** UDP Flood. Server stress test ****
        In(2): ***** UDP Flood. Server stress test ****
        In(3): ***** UDP Flood. Server stress test ****
        In(4): ***** UDP Flood. Server stress test ****
        In(5): ***** UDP Flood. Server stress test ****
        In(6): ***** UDP Flood. Server stress test ****
        Out(6): 
        In(6): ***** UDP Flood. Server stress test ****
        Out(6): 
        In(6): ***** UDP Flood. Server stress test ****
        Out(6): 
        In(6): ***** UDP Flood. Server stress test ****
        Out(6):

    Thank you so much!


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: NIO UDP DatagramChannel data not sending outů

    The program said that the port is in use.
    Has the program been executed more than once? Has the first execution stopped completely before the second one has started?
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: NIO UDP DatagramChannel data not sending outů

    Quote Originally Posted by Norm View Post
    Has the program been executed more than once? Has the first execution stopped completely before the second one has started?
    You mean the 3rd party test program that reads the OUT_PORT, or my Java program?
    There is only one instance running at the same time.
    Thank you so much.

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: NIO UDP DatagramChannel data not sending outů

    Have you checked that the port was not in use before starting your program?
    Could your program try to use the post more than once?
    If you don't understand my answer, don't ignore it, ask a question.

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