I have written a method to read the next incoming packet from a
non-blocking DatagramSocketChannel, convert it into a DatagramPacket and
return it. The method works perfectly the first time it is called, but
as soon as the method is called with NEW data waiting on the channel,
the data from the first message is returned. For example:

--Loop--
receiveFromSocket()
No data waiting, return null
--End Loop--
receiveFromSocket()
Data waiting from node1, return msg1
--Loop--
receiveFromSocket()
No data waiting, return null
--End Loop--
receiveFromSocket()
Data waiting from node2, return msg2
--Loop--
receiveFromSocket()
No data waiting, return null
--End Loop--
receiveFromSocket()
New data waiting from node1, still returns msg1, should return msg3

This happens every time, and I cannot figure out why the
DatagramSocketChannel is always returning the same data when a new
message is received from the same address. At the end of this message is
the method code. The entire source code is online at
http://code.google.com/p/waefers-bum/source/ . This method is inside
net.waefers.Messaging.MessageControl .

There is also a log file inside the default package. The software sends
a message from ReplicaMaster to NodeMaster successfully, and
ReplicaMaster receives the reply from NodeMaster successfully. However,
when TestPeer connects to NodeMaster successfully, and causes NodeMaster
to send a message to ReplicaMaster, ReplicaMaster receives the heartbeat
response packet again instead of the new data.

If you are intending to run the software and test it, first run
NodeMaster, then run ReplicaMaster. RM will heartbeat with NM. Finally,
run TestPeer. TP will attempt to heartbeat with NM. NM will attempt to
update block on RM, but RM will not receive the message and TP and NM
will continuously attempt to resend the (apparently) lost messages.

I hope the code is commented well enough easy understanding. If not,
please feel free to ask questions. I am working on this for a high
school independent study project, and I would really like to fix this
little bump in the road so I can move on with the software. I greatly
appreciate your time!

Sincerely,
Michael Ansel
news@anselcomputers.com

    private static DatagramPacket receiveFromSocket() throws IOException {
        synchronized(rbuf) {
            /* Clear the receive buffer before doing anything */
            rbuf.clear();
            /* Get the next packet */
            SocketAddress addr = server.receive(rbuf);
            if(addr == null) return null;
            /* Get the buffer ready for reading */
            rbuf.flip();
            /* Turn the data into a packet */
            DatagramPacket pkt = new DatagramPacket(rbuf.array(),rbuf.limit());
            pkt.setSocketAddress(addr);
           
            return pkt;
        }
    }