尝试从套接字读取时，非法的阻塞模式异常

Question

I am pretty new to Java and am trying to code a sender-channel-receiver setup, where the channel represents a transmission medium and introduces errors to the packets. So the channel is connected to the sender and the receiver using server socket channels. Most of it is fine, but when I attempt to read the object Packet within the channel, it throws IllegalBlockingModeException . The sender throws what seems to be a corresponding IO exception, "An existing connection was forcibly closed by the remote host". The code in the Channel program is as follows (some parts excluded for simplicity):

Set<SelectionKey> selectedKeys = selector.selectedKeys();
Iterator<SelectionKey> keyIterator = selectedKeys.iterator();
while (keyIterator.hasNext()) {
    SelectionKey key = keyIterator.next();
    keyIterator.remove();
    if (key.isAcceptable()) {
        SocketChannel sc = ((ServerSocketChannel) key.channel()).accept();
        sc.configureBlocking(false);
        sc.register(selector, SelectionKey.OP_READ);
    }
    if (key.isReadable()) {
        SocketChannel sc = (SocketChannel) key.channel();
        sc.configureBlocking(false);
        Packet packet = readPacket(sc);
        sc.close();
        // do things with the packet...

where readPacket is defined as follows:

private static Packet readPacket(SocketChannel sc) throws IOException, 
ClassNotFoundException {
    ObjectInputStream in = new 
    ObjectInputStream(sc.socket().getInputStream());
    Packet packet = (Packet) in.readObject();
    return packet;
}

is someone able to please explain what is throwing the exception and how to rectify it?

Answer 1

Streams are blocking. You cannot use them in non-blocking mode. See the Javadoc.