Retrieving Sender Information From A Non-blocking DatagramChannel

Bala <>
Mon, 24 Oct 2011 12:14:07 -0700 (PDT)
I have a DatagramChannel that I have added to a Java Selector. Hence
the configureblocking is set to false since the selector expects a non
blockign socket.
I have to use the DatagramChannel's receive call and cannot use the
socket.receive which reads the data in a packet due to the nonblocking

If I would have received / sent DatagramPacket using the
dc.socket().receive call, then the packet provides you the Sender
information anyways.

The problem is that I need the host/port of the sender from this
DatagramChannel. I see there are a couple of private variables within
the DatagramChannel class cachedSenderInetAddress, cachedSenderPort)
that have this information but those are private variables and I do
not see any method in the DatagramChannel or its socket to retrieve
the sender information.

Is there a way I can do this?

Here is the code snippet for the Receiver

class CReadDatagramChannel {

    DatagramChannel dc =;

    public CReadDatagramChannel (int port, Selector selector) {
        dc.socket().bind(new InetSocketAddress(port));
        dc.register(selector, SelectionKey.OP_READ, this);

    /* This method gets invoked from the Selector on the isReadable() */
    public void processRead () {
        // I cannot do dc.socket().receive(packet) since the blocking is
        ByteBuffer socketBuffer = ByteBuffer.allocate(1024);
        dc.receive (socketBuffer);

Here is the code snippet for the Sender

class CWriteDatagramChannel {
    DatagramChannel dc =;

    public CWriteDatagramChannel (int port, Selector selector) {
        dc.socket().bind(new InetSocketAddress(port));
        dc.register(selector, SelectionKey.OP_READ, this);

    /* This method gets invoked from the Selector on the isWritable() */
    pubic void processWrite (ByteBuffer writeBuffer, String host, int
port) {
        // I cannot do dc.socket().write since the blocking is false.
        dc.send(writeBuffer, new InetSocketAddress (host, port));

Is there a way to know the Sender after the receive call in the

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